Monitoring hybridization during PCR

Abstract: A method for detecting a target nucleic acid sequence in a biological sample during amplification comprising adding a thermostable polymerase and primers configured for amplification of the target nucleic acid to the biological sample, amplifying the target nucleic acid sequence by PCR in the presence of a heat labile double-strand specific dye, conducting the PCR through a number of amplification cycles, illuminating the biological sample comprising the amplified target nucleic acid sequence with light at a wavelength absorbed by the dye, and detecting a fluorescent emission from the dye related to the quantity of the amplified target nucleic acid sequence in the sample.

Description: This European Application is a divisional application of EP 97931089. This invention relates generally to observing fluorescence signals resulting from hybridization in conjunction with the polymerase chain reaction. More specifically, the present invention relates to observing hybridization with fluorescence during and/or immediately after PCR and using this information for product identification, sequence alteration detection, and quantification. The polymerase chain reaction (PCR) is fundamental to molecular biology and is the first practical molecular technique for the clinical laboratory. Despite its usefulness and popularity, current understanding of PCR is not highly advanced. Adequate conditions for successful amplifications must be found by trial and error and optimization is empirical. Even those skilled in the art are required to utilize a powerful technique without a comprehensive or predictive theory of the process. PCR is achieved by temperature cycling of the sample, causing DNA to denature (separate), specific primers to attach (anneal), and replication to occur (extend). One cycle of PCR is usually performed in 2 to 8 min, requiring 1 to 4 hours for a 30-cycle amplification. The sample temperature response in most RCR instrumentation is very slow compared to the times required for denaturation, annealing, and extension. The physical (denaturation and annealing) and enzymatic (extension) reactions in PCR occur very quickly. Amplification times for PCR can be reduced from hours to less than 15 min. Rapid cycling techniques are made possible by the rapid temperature response and temperature homogeneity possible for samples in high surface area-to-volume sample containers such as capillary tubes. For further information, see also: C.T. Wittwer, G.B. Reed, and K.M. Ririe, Rapid cycle DNA amplification, in K.B. Mullis, F. Ferre, and R.A. Gibbs, The polymerase chain reaction, Birkhauser, Boston, 174-181, (1994). Improved temperature homogeneity allows the time and temperature requiremants of PCR to be better defined and understood. Improved temperature homogeneity also increases the precision of any analytical technique used to monitor PCR during amplification. Fluorimetry is a sensitive and versatile technique with many applications in molecular biology. Ethidium bromide has been used for many years to visualize the size distribution of nucleic acids separated by gel electrophoresis. The gel is usually transilluminated with ultraviolet light and the red fluorescence of double stranded nucleic acid observed. Specifically, ethidium bromide is commonly used to analyze the products of PCR after amplification is completed. Furthermore, EPA 0 640 828 A1 to Higuchi & Watson, discloses using ethidium bromide during amplification to monitor the amount of double stranded DNA by measuring the fluorescence each cycle. The fluorescence intensity was noted to rise and fall inversely with temperature, was greatest at the annealing/extension temperature (50°C), and least at the denaturation temperature (94°C). Maximal fluorescence was acquired each cycle as a measure of DNA amount. The Higuchi & Watson application does not teach using fluorescence to monitor hybridization events, nor does it suggest acquiring fluorescence over different temperatures to follow the extent of hybridization. Moreover, Higuch & Watson fails to teach or suggest using the temperature dependence of PCR product hybridization for identification or quantification of PCR products. The Higuchi & Watson application, however, does mention using other fluorophores, including dual-labeled probe systems that generate flourescence when hydrolyzed by the 5'-exonuclease activity of certain DNA polymerases, as disclosed in US Patent No. 5,210,015 to Gelfand et al. The fluorescence observed from these probes primarily depends on hydrolysis of the probe between its two fluorophores. The amount of PCR product is estimated by acquiring fluorescence once each cycle. Although hybridization of these probes appears necessary for hydrolysis to occur, the fluorescence signal primarily results from hydrolysis of the probes, not hybridization, wherein an oligonucleotide probe with fluorescent dyes at opposite ends thereof provides a quenched probe system useful for defecting PCR product and nucleic acid hybridization, K.J. Livak et al., 4 PCR Math. Appl. 357-362 (1995). There is no suggestion of following the temperature dependence of probe hybridization with fluorescence to identify sequence alterations in PCR products. The specific hybridization of nucleic acid to a complementary strand for identification has been exploited in many different formats. For example, after restriction enzyme digestion, genomic DNA can be size fractionated and hybridized to probes by Southern blotting. As another example, single base mutations can be detected by "dot blots" with allele-specific oligonucleotides. Usually, hybridization is performed for minutes to hours at a single temperature to achieve the necessary discrimination. Alternately, the extent of hybridization can be dynamically monitored while the temperature is changing by using fluorescence techniques. For example, fluorescence melting curves have been used to monitor hybridization. L.E. Morrison & L.M. Stols, Sensitive fluorescence-based thermodynamic and kinetic measurements of DNA hybridization in solution, 32 Biochemistry 3095-3104, 1993). The temperature scan rates are usually 10°C/hour or less, partly because of the high thermal mass of the fluorimeter cuvette. Current methods for monitoring hybridization require a lot of time. If hybridization could be followed in seconds rather than hours, hybridization could be monitored during PCR amplification, even during rapid cycle PCR. The many uses of monitoring hybridization during PCR, as will be fully disclosed herein, include, product identification and quantification, sequence alteration detection, and automatic control of temperature cycling parameters by fluorescence feedback The prior art, as explained above, carries out temperature cycling slowly and empirically. When analysis of PCR products by hybridisation is needed, additional time consuming steps are required. Thus, it would be a great advance in the art to provide methods for monitoring hybridization during. PCR and analyzing the reaction while it is taking place, that is, during or immediately after temperature cycling without manipulation of the sample. By monitoring hybridization during PCR, the underlying principles that allow PCR to work can be followed and used to analyze and optimize the reaction during amplification. EP 0640 828A discloses an apparatus for monitoring multiple nucleic acid reactions simultaneously. It uses a thermal cycler and sensor for detecting light emitted from recesses in the thermal cycler. It is an object of the present invention to provide a double-strand-specific DNA dye for monitoring product hybridization during PCR. It is another object of the invention to provide a system for identifying PCR-amplified products by their fluorescence melting curves. It is also an object of the invention to provide a method for improving the sensitivity of PCR quantification with double-strand-specific DNA dyes. It is still another objection of the invention for determining the amount of specific product amplified by PCR by melting curves to correct for nonspecific amplification detected with the double-strand-specific DNA dye. It is a further object of the invention to provide a method of relative quantification of different PCR products with double-strand-specific dyes. It is yet another object of the invention to provide a method of product quantification by the reannealing kinetics of the product in the presence of a double-strand-specific DNA dye. It is also an object of the present invention to provide a method to determine initial template copy number by following the fluorescence of a hybridization probe or probes each cycle during PCR amplification. It is a further object of the invention to provide a system for relative quantification of different PCR products by probe melting curves. It is yet another object of the invention to provide methods to determine the initial template copy number by curve fitting the fluorescence vs cycle number plot. It is still another object of the invention to provide a system and method for performing PCR rapidly and also continuously monitoring the reaction and adjusting the reaction parameters while the reaction is ongoing. It is another object of the invention to replace the nucleic acid probes by synthetic nucleic acid analogs or derivatives, e.g. by peptide nucleic acids (PNA), provided that they can also be labeled with fluorescent compounds. These and other objects and advantages of the invention will become more fully apparent from the description and claims which follow, or may be learned by the practice of the invention. The present invention provides a method of real time monitoring of amplification of a target nucleic acid sequence in a biological sample, said method comprising the steps of: amplifying the target sequence by polymerase chain reaction in the presence of a quantity of SYBR™Green I, said polymerase chain reaction comprising the steps of adding the SYBR™Green I a thermostable polymerase, and primers for the target nucleic acid sequence to the biological sample to create an amplification mixture and thermally cycling the amplification mixture between at least a denaturation temperature and an elongation temperature during a plurality of amplification cycles; and either illuminating the mixture with a light at a wavelength absorbed by SYBR™Green I in at least a portion of the plurality of amplification cycles, and detecting a fluorescent emission from the SYBR™Green I following sample illumination, said fluorescent emission being related to the quantity of amplified target nucleic acid in the sample, Or illuminating the sample with light at a wavelength absorbed by the SYBR™Green I subsequent to at least a portion of the plurality of amplification cycles, and monitoring fluorescent emission from the SYBR™Green I in the sample as a function of the sample temperature to generate a melting curve for the amplified target sequence. The present invention also provides a PCR reaction mixture for amplifying a target nucleotide sequence, the mixture comprising a DNA sample having the target sequence oligonucleotide primers in an amount sufficient for PCR amplification, a thermostable polymerase and SYBR™ Green I in an amount capable of providing a fluorescence signal indicative of the concentration of the target sequence in said mixture. Preferably the invention is characterised by illuminating the mixture with light at a wavelength absorbed by SYBR™Green I in at least a portion of the plurality of amplification cycles, and detecting a fluorescent emission from the SYBR™Green I following sample illumination, said fluorescent emission being related to the quantity of amplified target nucleic acid in the sample, and further characterised by illuminating the sample with light at a wavelength absorbed by the SYBR™Green I subsequent to at least a portion of the plurality of amplification cycles, and monitoring fluorescent emission from the SYBR™Green I in the sample as a function of the sample temperature to generate a melting curve for the amplified target sequence. The method may be used to detect a target nucleic acid sequence in a biological sample during amplification using a rapid temperature cycling profile. Preferably the temperature cycling profile has a duration of less than 2 minutes. The sample is illuminated and fluorescence is detected as the temperature is increased, to generate a melting curve. The present invention particularly decreases the total time required for PCR amplification and analysis over prior art techniques while at the same time allowing the option of significantly increasing the quality of the reaction by optimizing amplification conditions. The present invention provides methods and applications for continuous fluorescence monitoring of DNA amplificatfon. Required instrumentation combines optical components with structures to provide rapid temperature cycling to continuously monitor DNA amplification by a variety of different fluorescence techniques. In one illustrative embodiment, fluorescence is acquired continuously from a single sample or alternately from multiple samples on a rotating carousel with all of the samples being simultaneously subjected to rapid thermal cycling. Further information on associated instrumentation can be found in the U.S. patent applications referenced above. In accordance with the present invention, fluorescence during DNA amplification was monitored by the double strand-specific dye SYBR Green I. Fluorescence data acquired once per cycle allow quantification of initial template copy number. Furthermore, in contrast to measuring fluorescence once per cycle, embodiments of the present invention are disclosed which monitor temperature, time and fluorescence continuously throughout each cycle thus producing a 3-dimensional spiral. This 3-dimensional spiral can be reduced to temperature vs. time, fluorescence vs. time, and fluorescence vs. temperature plots. Fluorescence vs. temperature plots of the fluorescence from hybridization probes can be used to detect sequence alterations in the product. These sequence alterations may be natural, as in mutations or polymorphisms, or artificial, as in an engineered alternative template for quantitative PCR. In accordance with a preferred aspect of the present invention, fluorescence monitoring is used to acquire product melting curves during PCR by fluorescence monitoring with SYBR™ Green I. Plotting fluorescence as a function of temperature as the thermal cycler heats through the dissociation temperature of the product gives a PCR product melting curve. The shape and position of this DNA melting curve is a function of GC/AT ratio, length, and sequence, and can be used to differentiate amplification products separated by less than 2°C in melting temperature. Desired products can be distinguished from undesired products, including primer dimers. Analysis of melting curves can be used to extend the dynamic range of quantitative PCR and to differentiate different products in multiplex amplification. Using the dye, product denaturation, reannealing and extension can be followed within each cycle. Continuous monitoring of fluorescence allows acquisition of melting curves and product annealing curves during temperature cycling. The present invention provides reagents and methods for rapid cycle PCR with combined amplification and analysis by fluorescence monitoring in under thirty minutes, more preferably in under fifteen minutes, and most preferably in under ten minutes. A method of real time monitoring of a polymerase chain reaction amplification of a target nucleic acid sequence in a biological sample comprises amplifying the target sequence by polymerase chain reaction in the presence of amplifying the target sequence by polymerase chain reaction in the presence of a quantity of SYBR™ Green I, said polymerase chain reaction comprising the steps of adding the SYBR™Green I a thermostable polymerase, and primers for the target nucleic acid sequence to the biological sample to create an amplification mixture and thermally cycling the amplification mixture between at least a denaturation temperature and an elongation temperature during a plurality of amplification cycles; and either illuminating the mixture with a light at a wavelength absorbed by SYBR™ Green I in at least a portion of the plurality of amplification cycles, and detecting a fluorescent emission from the SYBR™ Green I following sample illumination, said fluorescent emission being related to the quantity of amplified target nucleic acid in the sample, or illuminating the sample with light at a wavelength absorbed by the SYBR™ Green I subsequent to at least a portion of the plurality of amplification cycles, and monitoring fluorescent emission from the SYBR™Green I in the sample as a function of the sample temperature to generate a melting curve for the amplified target sequence. A PCR reaction mixture for amplifying a target nucleotide sequence comprising a DNA sample having the target oligonucleotide primers in an amount sufficient for PCR amplification, a thermostable polymerase and SYBR™ Green I in an amount capable of providing a fluorescence signal indicative of the concentration of the target sequence in said mixture. A method for analyzing a target DNA sequence of a biological sample comprises amplifying the target sequence by polymerase chain reaction in the presence of a nucleic acid binding fluorescent entity, said polymerase chain reaction comprising the steps of adding a thermostable polymerase and primers for the targeted nucleic acid sequence to the biological sample and thermally cycling the biological sample between at least a denaturation temperature and an elongation temperature; exciting the sample with light at a wavelength absorbed by the nucleic acid binding fluorescent entity; and monitoring the temperature dependent fluorescence from the nucleic acid binding fluorescent entity as temperature of the sample is changed wherein. The nucleic acid binding fluorescent entity comprises the double stranded nucleic acid binding fluorescent dye SYBR™ Green I. The temperature dependent fluorescence can be used to identify the amplified products, preferably by melting curve analysis. Relative amounts fo two or more amplified products can be determined by analysis of melting curves. For example, areas under the melting curves are found by non-linear least squares regression of the sum of multiple gaussians. BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS Original figures 6-14, 16-18, 33-36 and 46-48 have been deleted. Figures 1A&B are graphs representing an equilibrium PCR paradigm (A) and a kinetic PCR paradigm (B). Figure 2 illustrates useful temperature v. time segments for fluorescence hybridization monitoring. Figure 3 is a temperature v. time chart exemplary of rapid temperature cycling for PCR. Figure 4 shows the results of four different temperature/time profiles (A-D) and their resultant amplification products after thirty cycles (inset). Figures 5A, B & C illustrate the mechanism of fluorescence generation for three different methods of fluorescence monitoring of PCR: (A) double-stranded DNA dye, hybridization probes. Figure 15 is a fluorescence v. cycle number plot for a number of different initial template copy reactions monitored with Sybr™ Green I: 0, (Δ); 1, (▪); 10, (-); 10 2 , (-); 10 3 , (+); 10 4 , (); 10 5 , (⋄); 10 6 , (×); 10 7 , (▴); 10 8 , (□); 10 9 , (◆). Figures 19A-C provide a comparison of three fluorescence monitoring techniques for PCR, including the double-strand specific DNA dye SYBR Green I (A), a dual-labeled fluorescein/rhodamine hydrolysis probe (B), and a fluorescein-labeled hybridization probe with a Cy5-labeled primer (C); Figure 19D shows the coefficient of variation for the three monitoring techniques represented in Figures 19A-C. Figure 20 shows a typical log fluorescence vs cycle number plot of a standard amplification monitored with SYBR Green I. Figure 21 shows an expontial curve fit to cycles 20-27 or the data from Figure 20. Figure 22 shows an exponential fit to an unknown to determine initial copy number from amplification data. Figure 23 shows a typical fluorescence v. cycle number plot of five standards monitored each cycle with adjacent hybridization probes, wherein initial copy numbers are represented as follows: 10 3 , (); 10 4 , (⋄); 10 5 , (▴) 10 6 , (□); 10 7 , (◆). Figure 24 shows a curve fit to the standard data of Figure 23. Figure 25 shows a typical fluorescence vs cycle number plot of five standards monitored each cycle with a hydrolysis probe, wherein initial copy numbers are represented as follows: 1.5, (); 15, (⋄); 150, (▴); 1500, (□); 15,000, (◆). Figure 26 shows a curve fit to the standard data of Figure 25. Figure 27 shows a typical log fluorescence vs cycle number plot of three standard amplifications monitored with SYBR Green I, wherein: (▪); (); (▴). Figure 28 shows different curve fit to the standard data of Figure 27. Figures 29A&B show plots of (A) time v. fluorescence and (B) time v. temperature demonstrating the inverse relationship between temperature and fluorescence. Figure 30 is a chart showing 2D plots of temperature v. time, fluorescence v. time, and fluorescence v. temperature, also shown as a 3D plot, for the amplification of a 180 base pair fragment of the hepatitis B genome in the presence of SYBR Green I. Figure 31 is a fluorescence v. temperature projection for the amplification of a 536 base pair fragment of the human beta-globin gene in the presence of SYBR Green I. Figures 32A&B provide a plot showing (A) a linear change in fluorescence ratio with temperature for hydrolysis probes, and (B) a radical change with temperature for hybridization probes. Figure 37 shows melting curves for PCR-amplified products of hepatitis B virus (; 50% GC, 180 bp); beta-globin (▴; 53.2% GC, 536 bp); and prostate specific antigen (X; 60.38 GC, 292 bp). Figure 38 shows melting curves for PCR-amplified product of hepatitis B virus at heating rates of 0.1°C to 5.0°C. Figure 39 shows melting curves for PCR-amplified product of hepatitis B virus at various SYBR™ Green I concentrations. Figures 40A&B show (A) melting curves and (B) electrophoretically fractionated bands of products of a beta-globin fragment amplified with (a) no added template, (b) 10 6 copies of added template under low stringency conditions, and (c) 10 6 copies of added template under higher stringency conditions. Figures 41A&B show (A) melting curves and (B) melting peaks of hepatitis B virus fragment (HBV), β-globin, and a mixture thereof. Figures 42A-D show (A) a relative fluorescence v. cycle number plot for PCR amplified products from various amounts of β-globin template, (B) melting peaks and (C) electrophoretic bands of the various products, and (D) corrected fluorescence of the data of (A). Figures 43A&B show (A) melting curves and (B) melting peaks from PCR amplified products of a mixture of the cystic fibrosis gene and the c-erbB-2 oncogene. Figure 44 show melting peaks at various cycle numbers for the cystic fibrosis gene (CFTR) and c-erbB-2 (neu). Figure 45 shows a graph of integrated melting peaks of CFTR and neu PCT products. Figure 49 shows the shape of reannealing curves of amplified β-globin PCR products from various initial template amounts. Figure 50 shows the determination of a second order rate constant for determining initial template concentration. Figure 51 shows a block diagram for controlling thermal cycling from fluorescence data. Figures 52A&B show (A) a temperature v. time plot acquired after 20 cycles and (B) a fluorescence v. time plot acquired after 25 cycles wherein thermal cycling was controlled from fluorescence data. In describing and claiming the present invention, the following terminology will be used in accordance with the definitions set out below. As used herein, "nucleic acid," "DBA," and similar terms also include nucleic acid analogs, i.e. analogs having other than a phosphodiester backbone. For example, the so-called "peptide nucleic acids," which are known in the art and have peptide bonds instead of phosphodiester bonds in the backbone, are considered within the scope of the present invention. As used herein, "continuous monitoring" and similar terms refer to monitoring multiple times during a cycle of PCR, preferably during temperature transitions, and more preferably obtaining at least one data point in each temperature transition. As used herein, "cycle-by-cycle" monitoring means monitoring the PCR reaction once each cycle, preferably during the annealing phase of PCR. As used herein, "effective amount" means an amount sufficient to produce a selected effect. For example, an effective amount of PCR primers is an amount sufficient to amplify a segment of nucleic acid by PCR provided that a DNA polymerase, buffer, template, and other conditions, including temperature conditions, known in the art to be necessary for practicing PCR are also provided. PCR requires repetitive template denaturation and primer annealing. These hybridization transitions are temperature-dependent. The temperature cycles of PCR that drive amplification alternately denature accumulating product at a high temperature and anneal primers to the product at a lower temperature. The transition temperatures of product denaturation and primer annealing, depend primarily on GC content and length. If a probe is designed to hybridize internally to the PCR product, the melting temperature of the probe also depends on GC content, length, and degree of complementarity to the target. Fluorescence probes compatible with PCR can monitor hybridization during amplification. In accordance with the present invention, which is preferably used in connection with rapid cycling (fully described in the above-mentioned U.S. Serial No. 08/658,993, filed June 4, 1996, entitled System And Method. For Monitoring PCR Processes, and U.S. Serial No. 08/537,612, filed October 2, 1995, entitled Method For Rapid Thermal Cycling of Biological Samples), a kinetic paradigm for PCR is appropriate. Instead of thinking about PCR as three reactions (denaturation, annealing, extension) occurring at three different temperatures for three time periods (Figure 1A), a kinetic paradigm for PCR is more useful (Figure 1B). With a kinetic paradigm, the temperature vs. time curve consists of continuous transitions between overlapping reactions. Denaturation and annealing are so rapid that no holding time at a particular temperature is necessary. Extension occurs over a range of temperatures at varying rates. A complete analysis would require knowledge of all relevant rate constants over all temperatures. If rate constants of all reactions were known, a "physicochemical description of PCR" could be developed. Determining these rates would require precise sample temperature control and is greatly simplified by reaction monitoring during temperature cycling. Figure 2 illustrates useful temperature v, time segments for fluorescence hybridization monitoring. Product melting curves are obtained during a slow temperature increase to denaturation. By quickly lowering the temperature after denaturation to a constant temperature, product, probe, or primer annealing can optionally be followed. Probe melting curves are obtained by slowly heating through temperatures around the probe Tm. The embodiment represented in Figure 2 provides all analysis during temperature cycling with immediate real time display. Fluorescent probes are included as part of the amplification solution for continuous monitoring of primer, probe, or product hybridization during temperature cycling. The fluorescence hybridization techniques contained herein are based on rapid cycling, with its advantages in speed and specificity. A sample temperature profile during rapid cycle PCR is shown in Figure 3. Denaturation and annealing appear as temperature "spikes" on these figures, as opposed to the broad plateaus or conventional temperature cycling for PCR, e.g. Figure 1A. Rapid temperature cycling is contrasted to conventional temperature cycling in Figure 4, wherein it is shown that 30 cycles of amplification can be completed in 15 minutes and the resulting PCR products contain many fewer side products. Thus, with rapid cycling the required times for amplification are reduced approximately 10-fold, and specificity is improved. Example 1 Figure 4 shows the results of four different temperature/time profiles (A-D) and their resultant amplification products after thirty cycles (A-D). The profiles A and B in Figure 4 were obtained using a prior art heating block device using a prior art microfuge tube. As can be seen in Figure 4, the transitions between temperatures are slow and many nonspecific bands are present in profiles A and B. Profile B shows improvement in eliminating some of the nonspecific bands (in contrast to profile A) by limiting the time each sample remains at each temperature, thus indicating that shorter times produce more desirable results. Profiles C and D were obtained using a rapid temperature cycler. As can be seen in Figure 4, amplification is specific and, even though yield is maximal with 60-second elongation times (C), it is still entirely adequate with 10-second elongation times (D). The optimal times and temperatures for the amplification of a 536 bp fragment of beta-globin from human genomic DNA were also determined. Amplification yields and product specificity were optimal when denaturation (93°C) and annealing (55°C) were less than 1 second. No advantage was found to longer denaturation or annealing times. The yield increased with longer elongation times at 77°C, but there was little change with elongation times longer than 10-20 seconds. These unexpected results indicate that the previously available devices used for DNA amplification are not maximizing the conditions needed to optimize the physical and enzymatic requirements of the reaction. Further information can be obtained from: C.T. Wittwer et al., Rapid Cycle Allele-Specific Amplification with Cystic Fibrosis delta F(508) Locus, 39 Clinical Chemistry 804 (1993) and C.T. Wittwer et al., Rapid DNA Amplification, THE POLYMERASE CHAIN REACTION 174 (1994) The instrumentation used for fluorescence acquisition and rapid temperature cycling is fully disclosed in Serial No. 08/537,612, supra . As indicated earlier, the polymerase chain reaction can be performed rapidly. In addition to facilitating rapid heat transfer, the use of optically clear capillary tubes allows for continuous fluorescence monitoring of DNA amplification in accordance with the present invention. Fluorescent probes can be used to detect and monitor DNA amplification. Useful probes include double-stranded-DNA-specific dyes and sequence-specific probes. In Figure 5A, fluorescence depends on the hybridization of PCR product as detected with a double-strand-specific DNA dye. The method of Figure 5A is not sequence specific, although product specificity can be determined by melting curves, one aspect of the current invention. Double-strand-specific DNA dye selection. Those skilled in the art will be familiar with the use of ethidium bromide in fluorescence techniques. When a double strand-specific fluorescent dye is present during amplification, fluorescence generally increases as more double stranded product is made, see R. Higuchi et al., Simultaneous amplification and detection of specific DNA sequences, 10 Bio/Techaology 413-417 (1992). A fluorescence PCR assay for hepatitis C RNA using the intercalater, YO-PRO-1 is also known in the art. See T. Ishiguro et al., Homogeneous quantitative assay of hepatitis C virus RNA by polymerase chain reaction in the presence of a fluorescent intercalater, 229 Anal. Biochem. 207-213 (1995). It is preferred that SYBR™ Green I, which is well known in the art and available from Molecular Probes of Eugene, Oregon, be used as a - double-strand-specific dye. The molecular structure of this dye is a trade secret, but it is recommended by the manufacturer as a more sensitive double-strand-specific dye for DNA detection on gels. SYBR™ Green I is heat labile, however, and thus is not useful for fluorescence monitoring of PCR according to conventional methods where the temperature of the reaction mixture is maintained at melting temperatures for extended periods of time. Because of this heat lability, it was unexpected to discover that SYBR™ Green I can be used to monitor PCR reactions when melting, temperatures are not maintained for extended periods, i.e. when PCR is carried out by rapid cycling according to the kinetic paradigm described above. Example 2 Different double-strand-specific DNA dyes were compared by monitoring the amplification of a 110 base pair fragment from the PCO3/PCO4 primer pair of the human beta-globin gene from 10,000 template copies. Primers were synthesized by standard phosphoramidite chemistry as known in the art, namely, using Pharmacia Biotech Gene Assembler Plus (Piscataway, New Jersey). The human beta-globin primers PC03/PC04 (110 base pairs) are described in C.T. Wittwer et al., Automated polymerase chain reaction in capillary tubes with hot air, 17 Nucl. Acids. Res. 4353-4357 (1989), which is now incorporated herein by reference. DNA amplification was performed in 50 mM Tris, pH 8.5 (25°C), 3 mM MgCl 2 , 500 µg/ml bovine serum albumin, 0.5 µM of each primer, 0.2 mM of each deoxynucleoside triphosphate and 0.2 U of Taq polymerase per 5 µl sample unless otherwise stated in the following examples. Purified amplification product was used as DMA template and was obtained by phenol/chloroform extraction and ethanol precipitation, see D.M. Wallace, Large- and small-scale phenol extractions and precipitation of nucleic acids, 152 Methods in Enzymology 33-48 (1987), followed by removal of primers by repeated washing through a Centricon 30 microconcentrator (Amicon, Danvers, Massachusetts). Template concentrations were determined by absorbance at 260 nm. A(260):A(280) ratios of templates were greater than 1.7. SYBR™ Green I (Molecular Probes, Eugene, Oregon) was used at a 1:10,000 dilution, ethidium bromide was at 5 µg/ml, and acridine orange was at 3. µg/ml. These concentrations were determined to be optimal concentrations for maximizing the fluorescence signal observed during amplification for each dye. Excitation was through a 450-490 nm interference filter from a xenon arc source, except for ethidium bromide, where a 520-550 nm excitation was used. For SYBR™ Green I, the emmision at 520-550 was monitored. Ethidium bromide fluorescence was observed through a 580-620 nm bandpass. The acridine orange signal was taken as the ratio of green (520-550 nm) to red (>610 nm) fluorescence. The fluorescence of the sample before amplification was compared to the fluorescence after 35 cycles (94°C max, 60°C for 20 sec) at 60°C. The fluorescence increase was 5.3-fold for SYBR™ Green I, 1.7-fold for ethidium bromide, and 1.2-fold for acridine orange. In separate experiments, the fluorescence from SYBR™ Green I was stable for greater than 30 min at 70°C. It is also conveniently excited with visable light and is claimed to be less of a mutagen than ethidium bromide. Background fluorescence in all cases arose primarily from the primers. SYBR™ Green I is the double-strand-specific dye for fluorescence monitoring of PCR according to the present invention, primarily because of superior sensitivity, arising from greater discrimination between double stranded and single stranded nucleic acid. SYBR™ Green I can be used in any amplification and is inexpensive. In addition, product specificity can be obtained by analysis of melting curves, as will be described momentarily. Cycle-by-cycle fluorescence. Conventional endpoint analysis of DNA amplification by gel electrophoresis identifies product size and estimates purity. However, because amplification is at first stochastic, then exponential, and finally stagnant, the utility of endpoint analysis is limited for quantification. One aspect of the present invention includes cycle-by-cycle monitoring for quantification of initial template copy number with hybridization probes. As will be appreciated by those skilled in the art, once-per-cycle monitoring of multiple samples undergoing DNA amplification is a powerful quantitative tool. Cycle-by-cycle monitoring is achieved by acquiring fluorescence during the extension or combined annealing/extension phase of each cycle and relating the fluorescence to product concentration. Example 3 Cycle-by-cycle monitoring of PCR was performed by three different fluorescence techniques. Fluorescence was monitored by (i) the double-strand-specific dye SYBR™ Green I, (ii) a decrease in fluorescein quenching by rhodamine after exonuclease cleavage of a dual-labeled hydrolysis probe and (iii) resonance energy transfer of fluorescein to Cy5 by adjacent hybridization probes. However, the invention only includes monitoring of fluorescence by the double-strand-specific dye SYBR™ Green I. Amplification reagents and conditions were as described in Example 2. The human beta-globin primers RS42/KM29 (536 base pairs) and PC03/PC04 (110 base pairs) are described in C.T. Wittwer et al., Automated polymerase chain reaction in capillary tubes with hot air, 17 Nucl. Acids. Res. 4353-4357 (1989), which is now incorporated herein by reference. Temperature cycling for beta-globin was 95°C maximum, 61°C minimum, 15 sec at 72°C and an average rate between temperatures of 5.2°C/sec. The beta-actin primers and fluorescein/rhodamine dual probe were obtained from Perkin Elmer (no. N808-0230). Temperature cycling for beta-actin was 94°C maximum, 60°C for 15 sec with an average rate between temperatures of 6.2°C/sec. The single labeled probes 5'-CAAACAGACA CCATGGTGCA CCTGACTCCT GAGGA-fluorescein-3' (SEQ ID NO:3) and 5'-Cy5-AAGTCTGCCG TTACTGCCCT GTGGGGCAAGp (SEQ ID NO:4) were synthesized as in Example 3. These adjacent probes hybridize internal to the PC03/PC04 beta-globin primer pair on the same. DNA strand and are separated by one base pair. Temperature cycling was 94 °C maximum, 59 °C for 20 sec with an average rate between temperatures of 7.0°C/sec. Hybridization probes (beta-actin and beta-globin) were used at 0.2 µM each. When multiple samples are monitored once each cycle with SYBR™ Green I, a 10 7 -10 8 range of initial template concentration can be discerned as represented in Figure 15. This amplification is of a 536 base pair fragment of the beta-globin gene, with SYBR™ Green I as the double-strand specific dye. When the data were normalized as the percent maximal fluorescence of each sample, one hundred initial copies were clearly separated from ten copies. However, the difference between one and ten copies was marginal, and no difference was observed between zero and one average copies per sample. The fluorescence signal from hybridization probes is not cumulative and develops anew during each annealing phase. The fluorescence is a direct measure of product concentration because the hybridization is a pseudo-first order reaction. Because the concentration of probe is much greater than the product, the fraction of product hybridized to probe is independent of product concentration. These characteristics indicate that using a single hybridization probe along with a labeled primer will provide a superior monitor of product accumulation for quantification. The inherent variance of different fluorescence techniques during cycle-by-cycle monitoring is also important for quantification. Example 4 DNA amplification was perfomed according to Example 2 for each of three different fluorescence monitoring methods. SYBR™ Green I was used at a 1:10,000 dilution in the amplification of a 205 base pair human beta-globin fragment, from primers KM29 and PC04. The hydrolysis probe and conditions are those specified in Example 7. The hybridization probe, TCTGCCGTTA CTGCCCTGTG GGGCAAG-fluorescein (SEQ ID NO:5) was used with KM29 and the Cy5-labeled primer CAACTTCATCCACGTT*CACC (SEQ ID NO:6) where T* was a Cy5-labeled T base synthesized as in example 8. All amplifications were performed in ten replicates with 15,000 template copies (50 ng of human genomic DMA/10 µl). The temperature cycles were 31 sec long (94°C maximum, 60°C for 20 sec, average rate between temperatures 6.2°C/sec). Fluorescence was acquired for each sample between seconds 15 and 20 of the annealing/extension phase. Figure 19A allows comparison of three fluorescence monitoring techniques for PCR. The fluorescence probes are the dsDNA dye SYBR™ Green I (Figure 19A), a dual-labeled fluorescein/rhodamine hydrolysis probe (Figure 19B), and a fluorescein-labeled hybridization probe with a Cy5-labeled primer (Figure 19C). All probes had nearly the same sensitivity with detectable fluorescence occurring around cycle 20. With extended amplification, the signal continued to increase with the hydrolysis probe, was level with SYBR™ Green I, and slightly decreased with the hybridization probe. The precision of the three fluorescence monitoring techniques are compared in Figure 19D. The mean +/- standard deviations are plotted for each point. The data are plotted as the coefficient of variation (standard deviation/mean) of the fluorescence ratio above baseline (taken as the average of cycles 11-15). Although the change in fluorescence ratio from the hydrolysis probe is greater than that from the hybridization probe (Figures 19B and 19C), the coefficient of variation of fluorescence from the hydrolysis probes is greater (Figure 19D). That is, the fluorescence resulting from the hybridization probe method is more precise than using a hydrolysis probe, even though the absolute signal levels are lower. This is an unexpected advantage of hybridization probes over the more usual dual-labeled hydrolysis probes. Quantification of initial template copy number. Quantitative PCR has become an important technique in both biomedical research and in the clinical laboratory. The process of quantification often includes running a standard curve of samples containing known copy numbers of the target sequence. The copy number of an unknown sample is determined by extrapolation between the known values. When a complete amplification curve is monitored cycle-by-cycle using fluorescence, radioactivity or any other method that gives a signal proportional to the amount of DNA present, many data points are available for analysis and it is not obvious which value to choose to represent a standard or unknown.. Prior art is to choose a "threshold value" of the signal and then use the cycle number when the standard or unknown crosses that threshold as the representative value (see Higuchi & Watson, EPA 0 640 828 A1). This approach uses a very small amount of the available data in an amplification curve. In addition, the assignment of the threshold value is highly subjective and is subject to conscious or unconscious bias. More of the available data could be used objectively by applying non-linear curve fitting techniques to the data in an amplification curve. Preferably, equations could be found that describe the shape of the amplification curves by modeling factors of the underlying process. A number of different equations could be used to fit the data produced during amplification. DNA amplifications typically have a log linear segment and the data in this segment can be fit to an equation that describes an exponential increase like that expected in a DNA amplification. The log-linear portion of a DNA amplification can be described by the equation: y = A*[DNA]*(1+E) n wherein A is a scaling factor that converts units of signal to units of DNA; [DNA] is the starting concentration of DNA in the reaction; E is the efficiency of the reaction; and n is the cycle number. A quantification process would involve: (1) fitting the known standards to this equation allowing the parameters A and E to float, and (2) fitting the unknown samples to the equation using the values of A and E from the standards and allowing [DNA] to float. This technique uses much more of the data and uses the portion of the data, the log-linear portion, that is likely to be most informative. Figures 20, 21 and 22 show an example of this approach. Ten-fold dilutions of a purified PCR product were amplified as a standard curve and an "unknown" human genomic DNA standard was used. Figure 20 shows that the log-linear portion is easily identified either by the user or by software. Figure 21 shows a fit of the equation y=A*[DNA]*(1+E) n to the 10 4 copy standard. Figure 22 uses average values from several standards for A and E and fits [DNA]. The fit value of 16,700 is very close to the theoretical value for a single copy gene in genomic DNA (15,000 copies). Using all the data in an amplification curve would include the background level and the plateau value. While at high copy number the plateau is uninformative, at low copy number it is often proportional to starting copy number. The background level could be useful in determining the first point that shows a significant increase in signal. At this time all the factors involved in the shape of the DNA amplification curve are not known, so one approach is to describe the shape of the curve. Figure 23 shows amplification curves using fluorescent hybridization probes to detect a five order of magnitude range of DNA template concentrations. Each curve is fit to the equation: y=((as*x+ab)-(ds*x+db))/(1+(x/c)^b)+(ds*x+db) wherein "as" is the background of the slope line, "ab" is the y intercept of the background line, "ds" is the slope of the plateau line, "db" is the y intercept of the slope line, "c" is cycle number where the reaction is half way from background to plateau (A 50 ), and "b" is the slope of the log-linear portion of the amplification. This equation gives good fits to this amplification data, and Figure 24 shows that the value of the A 50 correlates well with the log of the starting copy number across seven orders of magnitude. Figure 25 shows the same equation fit to data from amplifications that used a hydrolysis probe to detect DNA template over a 5 order of magnitude range. This equation gives good fits to this amplification data, and Figure 26 shows that the value of the A 50 correlates well with the log of the starting copy number. This demonstrates the flexibility of the full curve fit approach as the equation has given good fits to both the sharp plateaus of the hybridization probe amplification curves and the steadily increaseing "plateaus" of the hydrolysis probe curves. Total curve fits are not limited to this equation. Figure 27 shows an amplification of three concentrations of DNA template fit to the equation: y=(((as*x+ab)-(dmax*x/dd+x)} / (1+(x/c)^b))+(dmax*x/dd+x), which is similar to the first 6 parameter equations except that the plateau is defined by a hyperbolic curve rather than by a line. Figure 28 shows that the A 50 for this equation correlates well to the starting copy number. While the A 50 has been used in these examples and level between the background and the plateau could be chosen if a particular technique is more robust lower or higher in the amplification profile. For example a series of amplification standard curves are evaluated for the best correlation between the starting copy number and the A 50 , the A 40 ,the A 30 the A 20 and the A 10 . The level of amplification that best correlates with the known starting copy number is determined. This will be different for different detections systems. Figure 19 shows that coefficient of variation for various detection systems. The level of amplification that is the best predictor is likely to be the level with the lowest coefficient of variation. As the DNA amplification reaction itself is better understood, other equations that have parameters that reflect physical processes could be used. The plateau of the DNA amplification curve has different causes in different reactions. It is often due to the inability of the primers to compete with product reannealing in the latter cycles. This effect could be captured with a parameter that is dependent on the square of the concentration of product in the reaction (as reannealing rate is proportional to the square of the product concentration). Another cause of the plateau can be the depletion of the primers. Primer limited reactions have a characteristic shape, they have a very sharp plateau that can be recognized. Primer limited reaction fits will include parameters that define this sharp top. Enzyme lifted reactions have a very rounded plateau that can be fit accordingly. Weighting factors can be devised that reflect the known coefficients of variation for the given system to more heavily weight the more reliable data points. By fitting more of the points in an amplification profile, more accurate and robust estimates of starting copy number can be obtained. One or more of the parameters of these fits can be used to estimate the starting copy number of unknown samples. Continuous fluorescence monitoring of PCR. The present invention's feature of continuous monitoring, that is, monitoring many times within each PCR cycle, will now be discussed. While fluorescence monitoring during PCR can be done once each cycle at a constant temperature, the present invention provides the important advantage of providing continuous monitoring throughout the PCR cycle. Temperature is important because fluorescence changes as the temperature changes. Figures 29A&B demonstrate the inverse relationship between temperature and fluorescence for SYB™ Green I. This is a confounding effect during temperature cycling that is usually eliminated by considering fluorescence once per cycle at a constant extension temperature. However, in accordance with the present invention, monitoring fluorescence during temperature changes is very informative. Prior to the present invention, continuous fluorescence monitoring within each cycle, as opposed to once each cycle, has not been carried out. In accordance with the present invention, time, temperature and fluorescence is acquired every sec, every 200 msec, every 100 msec or even at a greater frequency. Such data can reveal fine details of product denaturation, reannealing and extension, and probe annealing and melting during rapid cycling not available in previously available methods. Example 5 A 180-base-pair fragment of the hepatitis B surface antigen gene was amplified from 10 6 copies of purified PCR product using primers 5'-CGTGGTGGAC TTCTCTCAAT-3' (SEQ ID NO:1), and 5'-AGAAGATGAG GCATAGCAGC-3' (SEQ ID NO:2) (Genbank sequence HVHEPB). The amplification conditions of Example 2 were followed except that the reaction contained a 1:20,000 dilution of SYBR™ Green I and 2 mM MgCl 2 . Each temperature cycle was 27 sec long (92°C maximum, 59°C minimum, 5 sec at 70°C, average rate between temperatures 3.0°C/sec). Time, temperature, and 2 channels of fluorescence were acquired every 200 msec and continuously displayed as fluorescence v. cycle number and fluorescence v. temperature plots. Figure 30 shows a 3D trace of temperature, time and fluorescence ior cycles 10 through 34. This 3D curve is also projected in Figure 30 as 2D plots of temperature v. time, fluorescence v. time, and fluorescence v. temperature. The temperature v. time projection of Figure 30 repeats each cycle and provides essentially the same information as set forth in Figure 3. Because fluorescence varies inversely with temperature, the fluorescence v. time projection shown in Figure 30 at early cycles is a scaled mirror image of the temperature v. time plot (see Figure 29). As product accumulates, the fluorescence increases at all temperatures with double stranded product. However at denaturation temperatures, fluorescence returns to baseline since only single stranded DNA is present. The fluorescence v. temperature projection. of double stranded dyes shown in Figure 30 eliminates the time axis and shows the temperature dependence of strand status during DNA amplification. Example 6 A 536 base pair fragment of the human beta-globin gene was amplified from 25 ng of genomic DNA and a 1:10,000 dilution of SYBR™ Green I in a volume of 5 µl. Each temperature cycle was 28 sec long (95°C maximum, 61°C minimum, 15 sec at 72°C with an average rate between temperatures of 5.2°C/sec). Other conditions are the same as those described in Figure 30. Cycles 15-40 are displayed. The temperature dependence of product strand status during PCR is revealed by fluorescence v. temperature plots using as shown in Figure 31. Early cycles represented appear identical, with a nonlinear increase in fluorescence at lower temperatures. As amplification proceeds, temperature cycles appear as rising loops between annealing and denaturation temperatures. As the sample is heated, fluorescence is high until denaturation occurs. As the sample cools, fluorescence increases, reflecting product reannealing. When the temperature is constant during extension, increasing fluorescence correlates with additional DNA synthesis. As will be appreciated by an understanding of this disclosure, continuous monitoring within a cycle can provide insight into DNA amplification mechanics not previously available in the art. Using the present invention, many aspects of DNA amplification that have heretofore been little understood are discernable. For example, rapid cycle amplification claims to denature the product in less than one second, while the prior art uses ten seconds to one minute of denaturation. Observing product melting by real time fluorescences monitoring with double strand dyes in accordance with the present invention (Figures 30 and 31) shows that use of the shorter denaturation times is effective. As another example, many causes of the known "plateau effect" have been proposed, but few data are available to distinguish between alternatives. As shown in Figure 31, product reannealing is very rapid. In fact, during later cycles of amplification, a majority of product is reannealed each cycle during cooling before the primer annealing temperature is reached. This occurs with cooling rates of 5-10°C/sec in rapid cycle instrumentation. The product reannealing with slower, prior art temperature cyclers will be more extensive and this undesirable effect will be greater. Product reannealing appears to be a major, and perhaps the sole, cause of the "plateau effect." Now consider continuous monitoring of sequence specific probes. As will be appreciated by an understanding of this disclosure, continuous monitoring within a cycle can identity the nature of probe fluorescence. Example 7 Continuous monitoring of amplification every 200 msec was performed with a dual-labeled hydrolysis probe (beta-actin) and adjacent hybridization probes (beta-globin) as in Example 3. In Figure 32A, cycles 20-45 of a reaction monitored with the hydrolysis probe is shown. Hydrolysis probes show a linear change in fluorescence ratio with temperature and a parallel increase in fluorescence as more probe is hydrolyzed. In contrast, the fluorescence ratio from hybridization probes varies radically with temperature (Figure 32B, cycles 20-40). During the annealing/extension phase, the probes hybridize to single stranded product and the fluorescence ratio (Cy5/fluorescein) increases. During heating to product denaturation temperatures, the probes dissociate around 70°C, returning the fluorescence ratio to background levels. The present invention's combination of (1) continuous fluorescence monitoring within each temperature cycle and (2) analysis of the temperature and time dependence of hybridization provides advantages not otherwise obtainable. Figure 2 shows that information that was previously unobtainable can be extracted by continuous monitoring throughout the cycle. Continuous fluorescence monitoring during the product melting phase of the cycle provides useful information on the purity, identity, and quantity of DNA present during that cycle. As a PCR reaction is heated from the extension temperature to the denaturation temperature, any DNA in the sample is melted to single strands. This denaturation can be observed as a drop in the fluorescence of SYBR™ Green I. For small PCR products, the melting transition occurs over a narrow temperature range and the midpoint of that melting range is referred to as the Tm. Similar to sizing by gel electrophoresis, melting peak analysis measures a fundamental characteristic of DNA and can be used to identify amplified products. Unlike gel electrophoresis, melting curve analysis can distinguish products of the same length but different GC/AT ratio. In addition two products with the same length and GC content, but differing in their GC distribution (for example, equally distributed vs. a GC clamp on one end) would have very different melting curves. The temperature at which PCR products melt varies over a large range. Using empirical formulas known in the art, the effect of GC content on the melting temperature (Tm) of DNA predicts that a 0% GC duplex would melt 41° C lower than a 100% GC duplex. Given the same GC content, a 40 base pair primer dimer would melt 12°C below a 1000 bp product. Hence, the range of Tm for potential PCR products spans at least 50°C. This wide range allows most PCR products to be differentiated by melting curves. Thus, the combination of fluorescence monitoring of PCR with melting curve analysis provides simultaneous amplification, detection, and differentiation of PCR products. Example 8 DNA melting curves for three different PCR products were acquired on a microvolume fluorimeter integrated with a 24-sample thermal cycler with optics for SYBR™ Green I fluorescence (LightCycler LC24, Idaho Technology, Idaho Falls, Idaho). The primers for the 180 base pair hepatitis B surface antigen gene amplification were 5'-CGTGGTGGAC TTCTCTCAAT-3' (SEQ ID NO:1) and 5'-AGAAGATGAG GCATAGCAGC-3' (SEQ ID NO:2). The primers for the 292 base pair prostate specific antigen (PSA) gene amplification were 5'-CTGTCCGTGA CGTGGATT-3' (SEQ ID NO:7) and 5'-AAGTCCTCCG AGTATAGC-3'(SEQ ID NO:8). The 536 base pair human beta-globin gene amplification was done as in Example 3, PCR was performed as described in Example 2. Amplification products were purified by phenol/chloroform extraction and ethanol precipitation, followed by repeated washing through a Centricon 30 microconcentrator (available from Amicon of Danvers, Massachusetts). Template concentrations were determined by absorbency at 260 nm and had A(260)/A(280) ratios greater than 1.7. Fifty ng of purified DNA in 50 mM Tris, pH 8.5, 2 mM MgCl 2 , and 250 µg/ml bovine serum albumin and a 5 µl volume were pipetted into the open plastic reservoir of composite glass/plastic reaction tubes, centrifuged at low speed to place the sample at the tip of the glass capillary, and sealed inside with a plastic plug. Fluorescence data for melting curves was acquired by integrating the signal over 0.25 - 2.0 seconds during a linear temperature transition to 95°C at 0.1-10.0°C/second. The fluorescence was continuously acquired and displayed at fluorescence v. temperature plots in the LabView programming environment (National Instrument, Austin, TX). Figure 37 shows the melting curves of the three purified PCR products. The Tm's of three products in Figure 37 span only 6 degrees and two of the curves are separated by only 2 degrees. This small separation is ample to allow easy differentiation of the products. The importance of GC percentage over length on Tm is illustrated by the 292 bp PSA product melting at a higher temperature than the longer 536 bp beta-globin fragment. Melting curves are often obtained at rates of 0.5°C/minute to ensure equilibrium. Moreover, as the cheating rate decreases, the melting curve shifts to lower temperatures and becomes sharper (Figure 38; hepatitis B fragment). Note however, that the melting curves of Figure 37 were obtained during a heating rate of 0.2°C/sec (12°C/minute) and can differentiate products differing in Tm by 2°C or less. The apparent Tm of PCR products is also dependent on double-strand-specific DNA dye concentration (Figure 39, hepatitis B fragment). Higher concentrations of dye increase the stability of the DNA duplex and the observed Tm. For monitoring of melting curves with SYBR™ Green I, the preferred conditions are 1:7,000-1:30,000 fold dilution of SYBR Green I with heating rates of 0.1-0.5°C/second. These conditions allow easy differentiation of products that differ in Tm by 2° C. More precise temperature control and software for melting peak analysis will reduce the detectable difference in Tm to a fraction of a degree. This will allow the differentiation of most PCR products. Not all products can be differentiated by Tm however, just as it is possible to misread electrophoresis results because of comigration of two or more products, it is possible that some of the product melting in the expected range may not be the intended product. However, if no DNA melts in the range of the expected product, it can conclusively be said that none of the expected product is present. Another form of product differentiation available with melting curve analysis is the distinctive patterns of domain melting seen in longer PCR products. While short products (<300 bp) usually melt in one transition, longer products can have internal melting domains that give melting curves of a complex, distinctive shape. These complex melting curves can be used as a fingerprint for product identification. Melting curve analysis can be used to differentiate intended product from nonspecific products such as primer dimers. Primer dimers melt over a wide range of low temperatures; very different from the sharp melting curves of specific PCR amplification products. Larger heterogeneous products which resulted from running many cycles at low annealing stringency have lower and broader melting curves when compared with pure PCR product. Example 9 Amplification of the 536 beta-globin gene fragment was performed as in Example 3 with a 1:30,000 dilution of SYBR™ Green I except that the conditions were varied. In reaction A (Figure 40), no template was added and the reaction was cycled at 94°C for 0 sec, 60°C for 0 sec, and 72°C for 10 sec for 30 cycles to produce small nonspecific amplification products. In B, amplification of 10 6 initial copies of purified template at low stringency (94°C for 0 sec, 50°C for 0 sec, and 72°C for 10 sec) for 55 cycles showed a broad size range of amplification products on gel electrophoresis and melts across a wide temperature range. In C, 10 6 initial copies of purified template were cycled at 94°C for 0 sec, 60°C for 0 sec, and 72°C for 10 sec for 30 times and shows a single bright band and melts in a sharp transition. The temperature transition rate was 0.2°C/sec. A Hind III digest of λ phage DNA (M) is used as a marker. Figure 40 shows how melting curves accurately reflect the specificity of a PCR reaction. The sharp, high temperature melting curve C corresponds to a single band on a gel. The low temperature, broad melting, curve A comes from analysis of a no template control that shows only primer dimers. over-amplification of the product in C gives the intermediate melting curve B, still clearly differentiable from the specific product. The melting curves seen, for example, in Figure 37, can be better quantified by first taking the derivative of fluorescence (F) with respect to temperature (T). This derivative is plotted as dF/dT v. T and converts the melting curves to melting peaks. Example 10 The purified hepatitis B and beta-globin gene fragments of Example 8 were melted individually and together with a temperature transition rate of 0.2°C/sec and other conditions as specified in Example 8 (Figure 41). The somewhat subjective determination of Tm from the melting curves (top) is easily called by eye from the melting peaks (bottom). The area under the melting peaks can also be quantified by integration of the area under the curves. The fluorescence baseline was first subtracted from the -dF/dT v. T plot assuming that the magnitude of the baseline varies as the area under the curve. Then the peaks were fit by nonlinear least squares regression to gaussians with the mean, standard deviation, and height of the peak as the fit parameters. The area under each gaussian was taken as the peak area. All calculations were performed in the LabView programming environment (National Instruments, Austin, TX). Figure 41 shows an example of this conversion of melting curves to melting peaks. The code for these calculations is included as appendix A. The ability to distinguish specific product from primer dimer and other reaction artifacts improves the use of double-strand-specific DNA dyes in the quantification of low initial copy numbers. Relatively large initial template copy numbers have been quantified using ethidium bromide (Higuchi & Watson, supra ). However, at low initial copy numbers, the background amplification of primer dimers and other amplification artifacts interferes with the specific amplification signal. With the present invention's ability to differentiate specific products from non-specific artifacts, double-strand-specific DNA dyes can be used to quantify low initial template copy numbers. This is advantageous because of the simplicity of using these dyes. The double-strand-specific DNA dyes can be used in any amplification and custom fluorescently-labeled oligonucleotides are not necessary. Quantification of very low copy numbers with double-strand-specific DNA dyes requires very good amplification specificity or, as provided by the present invention, a means to differentiate the desired product from nonspecific amplification. Example 11 The present invention's approach to product purity determination was used to improve quantitative PCR based on once-per-cycle monitoring of double-strand-specific DNA dye fluorescence. Fluorescence was acquired once each cycle after polymerase extension of the product for a series of reactions varying in the initial concentration of purified beta-globin template (see Figure 42A). The beta globin template and amplification conditions were as given in Example 3. The log-linear increase above background fluorescence began at a cycle number dependent on initial template concentration. The plots of the five reactions ranging from 10 6 to 10 2 copies per reaction were separated by about four cycles. The sample with an average 10 2 copies per reaction showed a decrease in reaction efficiency, and reactions with initial copy number below 100 gave fluorescence profiles that were less useful. The fluorescence profiles for the reactions containing 10 and 1 (average) copies rise in reverse order, and the negative control showed amplification after about 30 cycles. This is due to amplification of primer dimers and other nonspecific amplification products that cannot be distinguished from the intended product by once-per-cycle fluorescence monitoring of double-strand-specific DNA specific dyes. Melting peaks were acquired for each sample (Figure 42B) and these were found to correlate well with electrophoresis results (Figure 42C). The reaction containing zero and one average initial template copies produced no discernible electrophoresis band at the expected 536 base pair location. The reactions containing 10 and 100 initial copies of template showed weak electrophoresis bands. This agreed well with the melting peak analysis, which showed no DNA melting in the range of the intended product (90 - 92°C) for the reactions containing zero and one initial copies and small peaks in this temperature range for 10 and 100 copies. Strong electrophoresis bands for the reactions containing 10 3 - 10 6 initial copies correlate well with large melting peaks in the expected 90 - 92°C range. The ratio of intended product to total product, determined by melting peak integration, ranged from 0.28 for 10 5 copies to 0.0002 for zero initial template copies. Each fluorescence value in Figure 41A was multiplied by the appropriate ratio to give the corrected plot (designated "corrected fluorescence" in Figure 42D). This procedure extended the effective dynamic range of quantitation to between 10 and 1 initial template copies. Melting peaks can distinguish specific products from non-specific products (Figure 40) and they can distinguish two purified PCR products mixed together (Figure 41) so they should also be useful for distinguishing two specific products amplified together in a single reaction tube. Melting curves obtained by continuous monitoring of PCR reactions according to the present invention are useful in multiplex PCR. Example 12 In this example, two gene fragments were simultaneously amplified from genomic DNA and monitored with SYBR™ Green I fluorescence. During each amplification cycle, different amplification products denature at melting temperatures dependent on the length of the product, GC ratio, and other factors well known in the art. The temperature at which each product melts can be monitored with the double-strand-specific dye, SYBR™ Green I. An 81 base pair fragment from the cystic fibrosis gene was amplified using the primers described herein as SEQ ID NO:14 and SEQ ID NO:15 along with a 98 base pair fragment of the c-erbB-2 (HER2/neu) oncogene using the primers described herein as SEQ ID NO:16 and SEQ ID NO:17. Amplification reactions were comprised of 50 mM Tris-HCl, pH 8.3, 3 mM MgCl 2 , 500 µg/ml of bovine serum albumin, 200 µM of each dNTP, and 0.5 µM of the cystic fibrosis primers, 0.3 µM of the HER2/neu primers, a 1:30,000 dilution of SYBR™ Green I, 1 U AmpliTaq Gold DNA polymerase (Perkin Elmer, Foster City, CA), and 50 ng of human genomic DNA in 10 µl. After activation of the polymerase at 95°C for 30 minutes, the samples were cycled at 94°C for 0 seconds (slope = 20), 55°C for 0 seconds (slope = 20), and 70°C for 10 seconds (slope = 20) for 35 cycles. The samples were cooled to 70°C, and the fluorescence was continuously acquired during a 0.2°C/sec ramp to 94°C. Melting curves (Figure 43) clearly showed two distinct products melting at 78°C (CFTR) and 89°C (neu). The two products differ in Tm by approximately 10°C and are easily distinguishable. Multiplex amplification is useful in cases where an internal control is needed during amplification. For example, many translocations are detectable by PCR by placing primers on each side of the breakpoint. If no amplification occurs, the translocation is not present as long as the DNA is intact and no inhibitor is present. These possibilities can be ruled out by amplifying a positive control locus in the same reaction mixture. Such control amplifications are best done as internal controls with simultaneous amplification and detection. Example 13 In this example, the procedure of Example 12 was followed except that after activation of the polymerase at 95°C for 30 minutes, the samples were cycled at 94°C for 0 seconds (slope = 20), 55°C for 0 seconds (slope = 20), and 70°C for 10 seconds (slope = 20) for 20 cycles, followed by 94°C for 0 seconds (slope = 1), 55°C for 0 seconds (slope = 20), and 70°C for 20 seconds (slope = 20) for 15 cycles. For cycles 26-31, fluorescence was continuously acquired during each 1°C/sec transition from 70°C to 94 °C. The melting curves were converted to melting peaks and displayed (Figure 44). Note that the amplification efficiency of the CFTR fragment appears greater than the neu fragment. The amplification efficiency can be rigorously determined by integrating the melting peak data as in Example 10. This kind of quantitative data referenced to a control has many applications. For instance, certain oncogenes, such as HER2/neu, are amplified in vivo in many tumors. That is, the genes are replicated in genomic DNA, sometimes many fold. Often, the clinical behavior of the tumor depends on the degree of oncogene replication. Amplification of the oncogene and a control template allows quantitative assessment of the relative copy number. As a further example, quantification of viral load in patients infected with HIV or hepatitis C is important in prognosis and therapy. Using a control template and monitoring the efficiency of amplification of both control and natural templates during amplification, accurate quantification of initial template copy number is achieved. The present invention's feature of using melting curves for relative quantification will now be explained. In accordance with the present invention, an additional use for melting curves is quantitative PCR. Figure 42 showed there was a correlation between the area under the melting peak and the amount of specific product. Relative quantification of two PCR products would be possible if the two produces were amplified with similar efficiency (or if the differing efficiencies were known and compensated for). Relative quantification of two products by integrating melting peak areas (see Example 10 is an aspect of the current invention. Example 14 The cystic fibrosis and HER-2-neu gene fragments of Example 12 were amplified, purified as in Example 2. and adjusted to 175 µg/ml. The samples were mixed in various ratios (total 8 µl) and added to buffer (1 µl) and SYBR™ Green I (1 µl). Final concentrations were 50 mM Tris, pH 8.3, 3 mM MgCl 2 , 250 µg/ml bovine serum albumin, and a 1:30,000 dilution of SYBR™ Green I. Melting curves were acquired at 0.2°C/sec, background fluorescence subtracted and the peaks integrated as described in Example 10. The results are displayed in Figure 45. Excellent correlation was found between the relative areas under melting peaks and the relative amounts of the two products. Relative quantification of two PCR products is important in many quantitative PCR applications. Multiplex amplification of two or more products followed by integration of the areas under the melting peaks will be extremely useful in these areas. mRNA is often quantified relative to the amount of mRNA of a housekeeping gene. Another important use of relative quantification is in competitive quantitative PCR. Typically a competitor is synthesized that has the same priming sites, but differs in length from the original target sequence. Known amounts of the competitor are spiked into an unknown sample and relative quantitation is performed. Competitors can be made that differ from the target sequence in Tm rather than length. The relative amounts of the products can be quantified by comparing the areas under their melting peaks. As the amount of one of the products is known, the quantity of the original target can be obtained. Using the melting peak method is significantly easier than the currently used methods which involve running multiple tubes for each unknown sample and often pulling tubes at various cycle numbers during the reaction to find the log-linear portion of the reaction. The relative amounts of the two products must then be determined. Usually this is done by labeling one of the dNTPs with a radioisotope and then quantifying ths amount of label incorporated into each band after agarose gel electrophoresis. In comparison, the current invention allows the reaction to be monitored continuously so the log-linear portion of the amplification can be easily identified. Relative quantification can be done quickly by integration of melting peaks. An all day process is reduced to less than an hour. From the foregoing discussion, it will be appreciated that fluorescence monitoring during DNA amplification is an extraordinarily powerful analytical technique. When sequence-specific detection and quantification are desired, resonance energy transfer probes can be used instead of double-strand-specific DNA dyes. The Tm of hybridization probes shifts about 4-8°C if a single base mismatch is present. If a hybridization probe is placed at a mutation site, single base mutations are detectable as a shift in the probe melting temperature. Absolute Product Concentration by Product Reannealing Kinetics. Product concentration determinations are also advantageously carried out using the present invention. Continuous monitoring of double stranded DNA formation allows DNA quantification at any cycle of amplification by reannealing kinetics. The sample temperature is quickly dropped from the denaturation temperature and held constant at a lower temperature that is still high enough to prevent primer annealing (Figure 2). The rate of product reannealing follows second order kinetics (see B. Young & M. Anderson, Quantitative analysis of solution hybridization. In: Nucleic Acid Hybridization: A Practical Approach 47-71 (B. Hames & S. Higgins, eds., (1985). For any given PCR product and temperature, a second order rate constant can be measured. Once the rate constant is known, any unknown DNA concentration can be determined from experimental reannealing data. Cooling is never instantaneous, and some reannealing occurs before a constant temperature is reached. Rapid cooling will maximize the amount of data available for rate constant and DNA concentration determination. The technique requires pure PCR product, but such can be assured by melting curves also obtained during temperature cycling using the present invention. This method of quantification by the present invention is advantageously independent of any signal intensity variations between samples. Example 15 A 536 base pair fragment of the beta-globin gene was amplified from human genomic DNA (Example 3) and purified (see Example 2). Different amounts of the purified DNA were mixed with a 1:30,000 dilution of SYBR™ Green I in 5 µl of 50 mM Tris, pH 8.3 and 3mM MgCl 2 . The samples were denatured at 94°C and then rapidly cooled to 85°C. The fluorescence at 520-550 nm was monitored at 85°C over time. When different concentrations of DNA were tested, the shape of the reannealing curve was characteristic of the DNA concentration (See Figure 49). For any given PCR product and temperature, a second order rate constant can be determined. Figure 50 shows the determination of a second order reannealing rate constant for 100 ng of the 536 base pair fragment in 5 µl at 85°C. The curve was fit by non-linear least squares regression with F max , F min , t 0 and k as the floating parameters using the second order rate equation shown in Figure 50. Analysis programs for this kind of curve fitting are well known in the art (for example, the user defined curve fit of Delta Graph, DeltaPoint, Inc, Monteray, CA). Once the rate constant is known, an unknown DNA concentration can be determined from experimental reannealing data. With the rate constant (k) defined, DNA concentrations are determined on unknown samples. The fluorescence vs time curves of unknown samples are fit by non-linear least squares regression, preferably during temperature cycling in real time (for example, using the nonlinear Levenberg-Marquardt method described in the LabView programming environment, National Instruments, Austin, TX). For this fit, F max , F min , t 0 , and [DNA] are the floating parameters and k is constant. Since some fluorescent dyes affect reannealing in a concentration dependent manner, the assumption of second order kinetics for product reannealing is checked by determining the rate constant at different standard DNA concentrations. The relationship is defined and alternate formula for fitting incorporated as necessary. Probe annealing rates are used to determine product concentration similar to the method described above for determining product concentration by product reannealing. The steps are summarized as follows: (1) choosing the appropriate rate equation for the system, (2) running known DNA standards to determine the rate constant, (3) checking the validity of the rate equation by comparing different rate constants derived from different concentrations, and (4) using the rates constants to determine the DNA concentration of unknowns from their probe annealing data. Fluorescence Feedback for Control of Temperature Cycling. In contrast to endpoint and cycle-by-cycle analysis, the present invention can also monitor fluorescence throughout each temperature cycle. Continuous fluorescence monitoring can be used to control temperature cycling parameters. The present invention uses fluorescence feedback for real time control and optimization of amplification. Continuous fluorescence monitoring of PCR samples containing a double-strand-specific DNA dye or fluorescently labeled oligonucleotide probes can be used to monitor hybridization and melting during individual amplification cycles. This information can be used by the temperature control algorithms within the temperature cycling apparatus to improve and customize thermal cycling conditions. Conventional PCR is performed by programming all cycling parameters before amplification. With continuous monitoring, determination of temperature cycling requirements can occur during amplification, based on continuous observation of annealing, extension, and denaturation. The potential benefits of using hybridization information to control temperature cycling include: 1. Ensuring complete denaturation of the PCR product each cycle while: a. Minimizing exposure to excessively high denaturation temperatures thus avoiding heat-induced damage to the amplification products and polymerase. Limiting the time product is exposed to denaturation temperatures is especially useful for amplification of long products. b. Increasing reaction specificity by minimizing the denaturation temperature. This selects against products with a Tm higher than the intended amplification product. 2. Maximizing the amplification efficiency by ensuring adequate time for primer annealing each cycle while: a. Minimizing the amount of time required for amplification by allowing no longer than is needed to reach a certain efficiency of primer annealing. b. Enhancing reaction specificity by minimizing the time at the annealing temperature. 3. Maximizing the amplification efficiency by ensuring adequate time for product extension each cycle while: a. Minimizing the amount of time required for amplification by allowing no longer than needed to complete product extension. b. Enhancing reaction specificity by selecting against products longer than the intended anfplification product. These would require longer than the allotted time to complete product extension. 4. Initiating thermal cycling changes dependent on the level of fluorescence obtained or the current efficiency of amplification. For example, over-amplification and nonspecific reaction products can be minimized by terminating thermal cycling when the efficiency drops to a certain level. As another example, temperature cycling can be modified to initiate slower temperature ramps for melting curve acquisition when the fluorescence becomes detectable. This saves time because the slower ramps need not be used on earlier cycles. Other desirable changes may become evident on continued practice of the invention. Control is based on an estimate of reaction parameters from the fluorescence data. The original fluorescence data is either acquired as a change in fluorescence over time (temperature specific rates of denaturation, annealing, and extension), a change in fluorescence over temperature (product or probe Tm), or a change in extent of amplification (amplification yield and efficiency). These rates, Tm's and their first and second derivatives are used to determine optimal reaction parameters that include denaturation temperature and time, primer annealing temperature and time, probe annealing temperature and time, enzyme extension temperature and time, and number of cycles. Double-strand-specific DNA dyes are used for the control of denaturation, control of extension, and to initiate thermal cycling changes at a certain amplification level or efficiency. Example 16 A commercial fluorescence monitoring thermal cycler (LC24 LightCycler, Idaho Technology Inc., Idaho Falls, Idaho) was modified so that the software is no longer programmed with temperature/time setpoints, but is programmed to acquire fluorescence values, then to use these values for thermal cycler control. As depicted in the Functional Block Diagram (Figure 51), the Run-Time Program communicates through serial and DAQ-board interfaces with the LightCycler. This allows high level access to either temperature or fluorescence data and either can be used by the Board-level Software for temperature control. However, in the current embodiment of the instrument, only the temperature data is converted into digital form at the Controller Hardware level. The fluorescence data is sent in analog form through the Digital acquisition board interface, is analyzed by the Run-time Program, and is sent back to the Board-level software via the serial interface. Product melting control: A melting peak was acquired for the intended PCR product and a baseline fluorescence was acquired for the sample containing the reaction cocktail at the temperature at which the product was completely melted. Each cycle of the reaction then used this fluorescence value as a target. The approach to product denaturation was made in two stages to overcome the time-lag due to the requirement of sending the fluorescence value to a remote computer for analysis, then returning the instruction that the value had been reached. With each product melting step, the temperature was increased until the fluorescence reached an intermediate value, then the heating power was reduced so that a temperature ramp rate of roughly 3°/sec gave the computer time to analyze the fluorescence and signal the thermal cycler that product denaturation had occurred. The resulting temperature/time plot (Fig 52) shows a characteristic increase in the melting temperature after cycle 20 as the concentration of amplification product increases. Product Tm is a function of product concentration. Product annealing/extension: During an extended hold at a combined annealing/extension temperature, the fluorescence was monitored and this information was used to ensure that adequate, but not excessive time had been allowed for product extension. The fluorescence was monitored at 10 second intervals, if the fluorescence increased more than a settable ratio (typically 1.00 - 1.05 ), then the annealing/extension step was continued. Otherwise, the next product melting step was initiated. The interval of 10 seconds was chosen to give a minimum of 20 seconds at the combined annealing/extension temperature. The resulting fluorescence/time plot (Fig 52) shows a characteristic increase in the dwell time at the combined annealing/extension temperature as the concentration of amplification product grows. As the primer concentration and polymerase become limiting, more time is needed to complete product extension with each cycle. Amplification plateau: At the end of each annealing/extension step, the fluorescence value was acquired and stored. When this value had increased to 1.2 times the lowest end-cycle fluorescence value and had subsequently stopped increasing below a user settable ratio (typically 1.00 - 1.02), the thermal cycling was terminated. Alternately, a melting-curve acquisition step was initiated by entering a slow 0.1 - 0.2°C/second temperature ramp through the product Tm and monitoring the fluorescence of the sample continuously. The resulting fluorescence/time plot (Fig 52) shows that after twenty-five cycles of amplification the ratio of cycle-by-cycle fluorescence growth fell below 1.00 and the reaction was terminated. In one embodiment of the present invention, detection of the amplification plateau is used to acquire a high-resolution melting curves for each sample in a multiple sample run at the optimal temperature cycle for each sample. As a sample reaches its amplification plateau, a melting-curve is acquired for that sample, then regular temperature cycling is resumed until another reaction reaches its amplification plateau. Summary. From the foregoing discussion, it will be appreciated that continuous fluorescence monitoring during DNA amplification to monitor hybridization is an extraordinarily powerful analytilcal technique. Using the methods described herein and depending on the number of initial template copies present, product identification and quantification can be achieved in five to twenty minutes after temperature cycling has begun. The present invention achieves several advantages not heretofore available in the art. For example, the present invention provides single-color fluorescence methods to monitor product purity, relative quantitation by multiplex PCR or competitive PCR, absolute product quantification by reannealing kinetics, and an improved method for initial template quantification by fluorescence vs cycle number plots. The following table describes double-strand-specific DNA dyes useful in continuous monitoring of PCR. The fluorescence of double-strand-specific DNA dyes depends on the strand status of the DNA. Summary of Fluorescent Probes for Continuous Monitoring of PCR dsDNA dye Hybridization Mechanism Strand status Probe Synthesis Unnecessary Specificity Product Tm Melting Analysis Yes Multicolor Analysis No In accordance with the present invention, time, temperature and fluorescence are acquired 1-10 times every sec and fine details of product and/or probe hybridization are observed during temperature cycling. With the double-strand-specific DNA dye SYBR™ Green I, the hybridization of product with respect to temperature is used to identify products by melting curves. In addition, relative product quantification is achieved by multiplex amplification of two or more different products that differ in Tm. Further, competitive PCR, is performed by altering the sequence internal to the common primers so that two or more products have different Tm's. Absolute product quantification is obtained by rapidly cooling the denatured product and observing reannealing kinetics. The sensitivity of initial template quantification with fluorescence vs cycle number plots is increased by analysis of product melting curves to control for nonspecific amplification and curve fitting algorithms. Finally, immediate fluorescence feedback for control of denaturation conditions, elongation times and product yield are obtained by monitoring product strand status with double-strand-specific DNA dyes. When multiplex analysis in one PCR reaction is desired, it is common practice to use different fluorescent labels with distinguishable emission spectra to identify the multiple products. The analysis is complicated by the limited number of fluorophores available and the overlapping emission spectra of those fluorophores that are available (see HM Shapiro, supra). Analysis of product or probe hybridization with melting curves is another method to distinguish multiple PCR products. By following hybridization during temperature cycling, the number of probes and/or spectral colors needed to distinguish multiple products can be minimized. Programming code for carrying out melting curve and other analyses is found on the following pages. SEQUENCE LISTING (1) GENERAL INFORMATION: (i) APPLICANT: Wittwer, Carl T. Ririe, Kirk M. Rasmussen, Randy P. (ii) TITLE OF INVENTION: Monitoring Hybridization During PCT (iii) NUMBER OF SEQUENCES: 27 (iv) CORRESPONDENCE ADDRESS: (A) ADDRESSEE: Thorpe, North & Western, L.L.P. (B) STREET: 9035 South 700 East, Suite 200 (C) CITY: Sandy (D) STATE: Utah (E) COUNTRY: USA (F) ZIP: 84070 (v) COMPUTER READABLE FORM: (A) MEDIUM TYPE: Diskette, 3.5 inch, 1.44 Mb storage (B) COMPUTER: Toshiba T2150CDS (C) OPERATING SYSTEM: Windows 95 (D) SOFTWARE: Word Perfect 7.0 (vi) CURRENT APPLICATION DATA: (A) APPLICATION NUMBER: (B) FILING DATE: (C) CLASSIFICATION: (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 08/658,993 (B) FILING DATE: 04-JUN-96 (vii) PRIOR APPLICATION DATA: (A) APPLICATION NUMBER: US 08/818,267 (B) FILING DATE: 17-MAR-97 (viii) ATTORNEY/AGENT INFORMATION: (A) NAME: Alan J. Howarth (B) REGISTRATION NUMBER: 36,553 (C) REFERENCE/DOCKET NUMBER: 8616.CIP7 (ix) TELECOMMUNICATION INFORMATION: (A) TELEPHONE: (801)566-6633 (B) TELEFAX: (801)566-0750 (2) INFORMATION FOR SEQ ID NO:1: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:1: (2) INFORMATION FOR SEQ ID NO:2: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:2: (2) INFORMATION FOR SEQ ID NO:3: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 35 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:3: (2) INFORMATION FOR SEQ ID NO:4: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 30 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:4: (2) INFORMATION FOR SEQ ID NO:5: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 27 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION; SEQ ID NO:5: (2) INFORMATION FOR SEQ ID NO:6: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:6: (2) INFORMATION FOR SEQ ID NO:7: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 18 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:7: (2) INFORMATION FOR SEQ ID NO:8: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 18 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:8: (2) INFORMATION FOR SEQ ID NO:9: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 46 base pairs (B) TYPE: mucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:9: (2) INFORMATION FOR SEQ ID NO:10: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 46 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:10: (2) INFORMATION FOR SEQ ID NO:11: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:11: (2) INFORMATION FOR SEQ ID NO:12: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:12: (2) INFORMATION FOR SEQ ID NO:13: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 23 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:13: (2) INFORMATION FOR SEQ ID NO:14: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:14: (2) INFORMATION FOR SEQ ID NO:15: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:15: (2) INFORMATION FOR SEQ ID NO:16: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:16: (2) INFORMATION FOR SEQ ID NO:17: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:17: (2) INFORMATION FOR SEQ ID NO:18: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 31 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:18: (2) INFORMATION FOR SEQ ID NO:19: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 26 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:19: (2) INFORMATION FOR SEQ ID NO:20: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 26 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:20: (2) INFORMATION FOR SEQ ID NO:21: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:21: (2) INFORMATION FOR SEQ ID NO:22: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 27 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:22: (2) INFORMATION FOR SEQ ID NO:23: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 32 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:23: (2) INFORMATION FOR SEQ ID NO:24: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 30 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:24: (2) INFORMATION FOR SEQ ID NO:25: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 23 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:25: (2) INFORMATION FOR SEQ ID NO:26: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 25 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:26: (2) INFORMATION FOR SEQ ID NO:27: (i) SEQUENCE CHARACTERISTICS: (A) LENGTH: 20 base pairs (B) TYPE: nucleic acid (C) STRANDEDNESS: single-stranded (D) TOPOLOGY: linear (xi) SEQUENCE DESCRIPTION: SEQ ID NO:27:

Claims: A method of real time monitoring of amplification of a target nucleic acid sequence in a biological sample, said method comprising the steps of: amplifying the target sequence by polymerase chain reaction in the presence of a quantity of SYBR™ Green I, said polymerase chain reaction comprising the steps of adding the SYBR™ Green I, a thermostable polymerase, and primers for the target nucleic acid sequence to the biological sample to create an amplification mixture and thermally cycling the amplification mixture between at least a denaturation temperature and an elongation temperature during a plurality of amplification cycles; and either illuminating the mixture with light at a wavelength absorbed by SYBR™ Green I in at least a portion of the plurality of amplification cycles, and detecting a fluorescent emission from the SYBR™ Green I following sample illumination, said fluorescent emission being related to the quantity of amplified target nucleic acid in the sample, or illuminating the sample with light at a wavelength absorbed by the SYBR™ Green I subsequent to at least a portion of the plurality of amplification cycles, and monitoring fluorescent emission from the SYBR™ Green I in the sample as a function of the sample temperature to generate a melting curve for the amplified target sequence. The method according to claim 1 characterised by illuminating the mixture with light at a wavelength absorbed by SYBR™ Green I in at least a portion of the plurality of amplification cycles, and detecting a fluorescent emission from the SYBR™ Green I following sample illumination, said fluorescent emission being related to the quantity of amplified target nucleic acid in the sample, and further characterised by illuminating the sample with light at a wavelength absorbed by the SYBR™ Green I subsequent to at least a portion of the plurality of amplification cycles, and monitoring fluorescent emission from the SYBR™ Green I in the sample as a function of the sample temperature to generate a melting curve for the amplified target sequence. A method according to claim 1 or 2 for detecting a target nucleic acid sequence in a biological sample during amplification using a rapid temperature cycling profile. The method of claim 3 wherein each cycle of the rapid temperature cycling profile has a duration of less than 2 minutes. The method of claim 3 wherein the sample is illuminated and fluorescence is detected as the temperature is increased, to generate a melting curve. A PCR reaction mixture for amplifying a target nucleotide sequence, the mixture comprising a DNA sample having the target sequence oligonucleotide primers in an amount sufficient for PCR amplification, a thermostable polymerase and SYBR™ Green I in an amount capable of providing a fluorescence signal indicative of the concentration of the target sequence in said mixture.

Inventors: RASMUSSEN RANDY P, RIRIE KIRK M, WITTWER CARL T, RASMUSSEN, RANDY P., RIRIE, KIRK M., WITTWER, CARL T.
Applicants: UNIV UTAH RES FOUND, UNIVERSITY OF UTAH RESEARCH FOUNDATION
Application year: 1997
Main classification: C12Q1
IPC codes: B01L3, C12Q1, G01N21, B01L7