bluuebunny/crossref_metadata_2025_split huggingface dataset:
Gene conversion in higher organisms: Non-reciprocal recombination events at the rosy cistron inDrosophila melanogaster
Authors: Ballantyne G. H. , Chovnick Arthur 
Published: September 2009

SUMMARYAnalysis of a series of exceptionalry+half-tetrads, produced in mass matings involving rosy mutant heterozygous half-tetrads, provides rigorous demonstration of the occurrence of non-reciprocal as well as reciprocal recombination events within the rosy cistron ofDrosophila melanogaster. Inferences about allele recombination drawn from this and other studies in Drosophila provide a strong argument that gene conversion occurs as a regular event in higher eukaryotes.
Development and complementation of lethal mutations at the dumpy locus ofDrosophila melanogaster
Authors: Metcalfe Judith A. 
Published: September 2009

SUMMARYThe genetical and developmental aspects of six dumpy mutants ofDrosophila melanogasterhave been investigated. The mutantsobm,lmandolv(possibly alleles),lv, lv1andlvI(possibly alleles) were known to be lethal when homozygous. Previously the lethal effect has been treated as a uniform effect. However, the lethal stage is not the same for all homozygotes, being egg/larval (E/L) for the threelvalleles, egg (E) forolv, larval/larval ecdysis (L/L) forlmand E/L and larval (L) forobm. Not all heterozygous combinations are lethal, i.e.obm/lmandobm/lvIare not lethal. Phenotypically the lethal heterozygotes fall into two patterns: (i) combinations not involving the alleleobmand (ii) combinations involvingobm. In the former, the mutant with the developmentally later expression is ‘dominant’ to the mutant with the developmentally earlier expression. In the latter, the genotypes manifest different proportions of individuals at the lethal stages E, E/L and L. Previous observations suggested that the lethality of the homozygoteobm/obmwas associated with the presence of an independent lethal in the stock. Observations presented here suggest that the lethality is a function of theobmallele itself. Complementation between some of the lethal mutants is not in accordance with the general rule for dumpy that compounds manifest the traits they have in common.
Genetic analysis ofsulmutants ofEscherichia coliB
Authors: Donch John J. , Chung Young Sup , Green Michael H. L. , Greenberg Joseph , Warren Guylyn 
Published: September 2009

SUMMARYThesulgene of B/rw (Witkin) and 26 independently isolatedsulmutants were examined for their suppression of radiation sensitivity. The suppressedlongene was demonstrated by transducing it into a K12proCrecipient. Thesulgene of B/rw and all but one of the B/r mutants was found to be linked to a gene controlling azide resistance. Transduction data established the order of markers asleu azi mutT sul. One B/r mutant was found not transducible with azide resistance,sulmutations were found to suppress the capsular polysaccharide production oflonstrains.
Biochemical investigation of the slow-growing non-perithecial (sgp) mutants ofAspergillus nidulans
Authors: Houghton J. A. 
Published: September 2009

SUMMARYUsing polarography the uptake of oxygen by intact and homogenized mycelium of a wild-type strain and strains of slow-growing non-perithecial (sgp) mutants was compared. It was found that whilst the oxygen uptake of intact, wild-type mycelium increased on the addition of glucose or succinate as substrate, uptake of oxygen by mutant mycelium increased only when glucose was used as substrate and was unaffected by succinate. When, however, homogenates of mutant mycelium were used oxidation of the succinate occurred. It was concluded that the inability of the mutants to utilize succinate was due to their impaired ability to take up the compound across the hyphal wall and this was confirmed using radioactively labelled substrates. It is tentatively suggested that the abnormal growth of thesgpmutants on glucose medium and their impaired permeability to tricarboxylic acid cycle intermediates may be due to reduced availability of high energy compounds caused by a lesion in their oxidative phos-phorylation system.
A technique for replica platingCoprinus lagopus, a filamentous fungus
Authors: Kaplan Philippa J. , Walls D. 
Published: September 2009

SUMMARYThe problem of replica plating filamentous fungi such asCoprinus lagopusis overcome by inducing micro-colonies with sodium deoxycholate and using ‘Velcro’, a hooked material, to replace velveteen in the standard replica plating technique. ‘Velcro’ is advantageous in that it has a regular pattern of closely spaced hooks which transfer small inocula from the colonies on the master plate.
The nature of the purebred-crossbred genetic covariance
Authors: McNew Ronald W. , Bell A. E. 
Published: September 2009

SUMMARYEpistatic models are examined for conditions which result in a negative covariance between a sire's purebred and test-cross progenies. It is found that heterozygote superiority is not a necessary condition for its occurrence. The frequencies of the same allele in the selected population and in the tester should be divergent. The implications of using the covariance in prediction are discussed. The important result to note is that selection in the crossbred may not be optimum even with a negative covariance.
Isoenzymes and polyploidy I. Qualitative and quantitative isoenzyme studies in the Triticinae
Authors: Mitra R. , Bhatia C. R. 
Published: September 2009

SUMMARYIsoenzymes of alcohol (ADH), malate (MDH), glutamate (GDH) and isocitrate (IDH) dehydrogenases, and a fast migrating esterase (EST-l) were separated by disk electrophoresis from dry seed extracts of diploid, tetraploid, hexaploid and octaploid species or amphiploids belonging to the subtribe Triticinae. Only ADH and EST-l isoenzymes showed inter-species variation; the other dehydrogenases, which show stringent substrate specificities (‘critical’ enzymes), revealed the same pattern in all diploid and polyploid species. The qualitative zymogram studies showed that (1) the number of variant enzyme bands increased with the level of ploidy, (2) the amphiploid isoenzyme pattern was additive of the parental species, (3) enhancement in the number of bands was due to the presence of not only parental bands, but also hybrid bands formed by association between heteromonomers. Quantitative data were obtained by densitometry of the enzyme bands as well as spectrophotometric measurements of enzyme activity in crude extracts. Increase in the level of enzyme activity was observed with ploidy level. In spite of the evidence that all duplicate/triplicate genes are expressed, increased enzyme activity observed in the polyploid species was not proportional to the level of ploidy or expected gene dosage. On the basis of ADH and EST-l zymograms obtained in 2 × and 4 × wheat, probable zymograms for these enzymes in the B-genome donor to 4 × wheat were extrapolated. NeitherAe. speltoidesnorAe.bicornisshowed the extrapolated ADH pattern. Amphiploids involvingAe.speltoidesandTriticum monococcumorT. aegilopoidesfully reproduced the EST-l zymogram of 4 × wheat, but not the ADH.Ae. bicornis×T. aegilopoidesamphiploid showed an ADH zymogram similar to that of 4 × wheat, but the EST-l bands were different.
Genes and genotypes affecting embryonic fluid relations in the mouse
Authors: Johnson D. R. 
Published: September 2009

SUMMARYThe contribution of maternal and foetal genotype to the regulation of extra-embryonic (exocoelomic and amniotic) fluid and embryonic fluid in the mouse is discussed. Three of the four inbred strains studied (A, BALB/c and CBA) had similar patterns of fluid accumulation. The fourth (C57BL) differed significantly. In the reciprocalF1crosses between CBA and C57BL a maternal effect was present. In theF2no increase in variance of extra-embryonic fluid was noted.The effects of two mutant genes were studied. Blebs (my) had no effect on the total fluid in the conceptus, but led to a rearrangement of fluid within the embryo. Brachyphalangy (Xtbph) caused an overall increase in fluid within the conceptus. Distribution of the excess depended upon the phenotype (exencephalic versus non-exencephalic) of the embryo.
Recombination and chromosome structure in eukaryotes
Authors: Putrament Aleksandra 
Published: September 2009

SUMMARYAllelic recombination frequency and pattern in fungi show strong gene-to-gene variation. At least in two fungal species,NeurosporaandSchizophyllum, recombination frequencies in certain chromosomal segments are genetically determined. The possibility that chromosomal proteins and/or synaptinemal complexes may play an important role in regulation of recombination frequency and pattern is discussed.
An estimate of heterosis inDrosophila melanogaster
Authors: Sved J. A. 
Published: September 2009

SUMMARYTwenty-five population cages ofD. melanogasterwere set up, each containing a different wild-type second chromosome and the marker chromosomeCy. In all but one case where contamination apparently occurred, theCychromosome persisted in the population at high frequency, showing a selective advantage ofCy/ + heterozygotes over wild-type homozygotes. Overall, the results indicate that homozygosity of the entire second chromosome causes a depression in fitness of the order of 85%.
The flagella of temporary dikaryons ofChlamydomonas reinhardii
Authors: Starling David , Randall John 
Published: September 2009

SUMMARYThe structure and function of flagella are genetically determined and single gene mutants – for example, lacking in motility or of abnormal flagellar length – have previously been investigated. When such mutants are crossed with wild-type, temporary dikaryons – prozygotes – are formed with two nuclei and a common cytoplasm. The properties of the four flagella – two originally abnormal – have been observed as a function of time. In wild-type × non-motile mutant crosses, restoration of motility has been observed in a number of cases. If the dikaryons are deflagellated regeneration occurs, together with restoration of motility or of normal length to the previously abnormal pair. Complementation at the cytoplasmic level has been found in paired mutants.
Further observations on the correlation between kappa and phage-like particles in paramecium
Authors: Grimes Gary W. , Preer John R. 
Published: September 2009

SUMMARYIt has been possible to examine the correlation between the presence of phage-like particles and R bodies by using serial sections of kappas of stock 562. No exception has been found to the rule that 562 kappa particles with R bodies also have phage-like particles; however, 3 out of 78 kappa particles with phage-like particles lacked R bodies.
Rates of spontaneous mitotic recombination inSaccharomyces cerevisiae
Authors: Thornton R. J. , Johnston J. R. 
Published: September 2009

SUMMARYThe rates of mitotic recombination at the lociade3,ade5–7,ade6andade8were approximated by the method of ‘increasing proportion of variants with growth’. The values (per cell generation) were 3·5 × 10−4forade8, 1·4 × 10−4forade5–7, 4·0 × 10−5forade3and < 2 × 10−6forade6. The relative frequencies of mitotic recombination in regions betweenade 5–7and the centromere were different from those obtained with radiation-induced recombinants.
Multiple recombinational events within the84 Wlocus ofAscorolus immersus
Authors: Paszewski A. , Prażmo W. , Jaszczuk E. 
Published: September 2009

SUMMARYMultiple recombinational events within a gene were studied by tetrad analysis of multipoint intragenic crosses. It was found that a considerarle proportion of double-site conversions can arise as two separate but correlated events. The same was true for conversion and crossing-over associated with it. The data point to a possibility of multiple recombinational events involving both conversions and cross-overs, occurring as successive rounds of recombination within a single recombinational process. Some of the results suggest that more than two chromatids may be involved in such a process. The results are discussed in terms of different recombination models.
Wheat mutants permitting homoeologous meiotic chromosome pairing
Authors: Wall A. M. , Riley Ralph , Chapman Victor 
Published: September 2009

SUMMARYPlants of Triticum aestivum (2n = 6x = 42) ditelocentric 5BL were treated with EMS in order to produce mutations in the 5B system by which meiotic pairing between homoeologous chromosomes is normally prevented. To check for the occurrence of mutation T. aestivum ditelo-5BL plants were pollinated with rye (Secale cereale 2n = 14) and meiosis was examined in the resulting hybrids.Wheat-rye hybrids were scored for the presence of mutants when the wheat parents were either the EMS-treated wheat plants, or their selfed derivatives, or their progenies obtained after pollination with untreated euploid individuals.Mutants were detected by each of these procedures and mutant gametes were produced by the treated ditelocentric plants with frequencies between 1·5 and 2·5%, but there were differences between the mutants in the extent to which homoeologous pairing occurred in the derived wheat-rye hybrids. The differences may have resulted from the occurrence of mutation at different loci or to different extents at the same locus.Two mutants, Mutant 10/13 and Mutant 61, were fixed in the homozygous condition. Mutant 10/13 was made homozygous both in the 5BL ditelocentric and in the euploid conditions but these genotypes regularly formed 21 bivalents at meiosis, and there was no indication of homoeologous pairing although the mutant 10/13 gave rise to homoeologous pairing in wheat-rye hybrids.
A simple technique for the identification of chain termination suppressor mutants in species ofSalmonella
Authors: Hedges R. W. 
Published: September 2009

SUMMARYChain-termination suppressors which are almost certainly amber suppressors have been isolated inSalmonella anatumby a technique involving the use of amber mutants of bacteriophage 01. The same technique could be used in any species ofSalmonella(and many strains of Arizona) and analogous techniques are suggested for use in other genera of bacteria and in higher plants.
The genetic analysis of the direct and correlated response to selection for chaetae inDrosophila melanogaster
Authors: Scowcroft W. R. 
Published: September 2009

SUMMARYThe direct and correlated response to selection of scutellar microchaetae and scutellar bristles has been analysed by determining the contribution of the three major chromosomes, alone and in combination with each other, to the overall response. The results of the analysis confirm a previous finding, based on a formal statistical approach, that response to selection for microchaetae had highly pleiotropic effects on scutellar bristles. In lines selected, each for high and low microchaetae, genetic changes in the 2nd and 3rd chromosomes are pre-eminent and essentially equal. Inter-chromosomal interactions are of relatively minor importance in interpreting the response to selection for microchaetae but assume greater importance with respect to the correlated character. The results are discussed in terms of the genetic correlation between fitness and the character measured.
The maintenance of the genetic variability of polygenic characters by heterozygous advantage
Authors: Bulmer M. G. 
Published: September 2009

SUMMARYThe results of a previous paper on the effect of optimizing selection, mutation and drift on a metric character determined by a large number of loci have been extended to include the possibility that, in addition to selection for an optimal value, there may be independent selection in favour of heterozygotes; it is assumed for simplicity that at each locus the heterozygote has the same advantage,s, over each of the homozygotes. Under selection alone there is a stable equilibrium ifs>ca2, wherecis a measure of the intensity of the optimizing selection andais the effect of a gene substitution. Under the additional forces exerted by mutation and by drift due to finite population size each locus behaves independently of the other loci as if it had a heterozygous advantage equal to (s−ca2).
Genetic differences between populations of Drosophila melanogaster for a quantitative trait: II. Wild and laboratory populations
Authors: López-Fanjul C. , Hill W. G. 
Published: September 2009

SUMMARYCrosses were made between four populations of Drosophila melanogaster – three of which were laboratory populations (Kaduna, Pacific and Canberra) and one recently captured (Stellenbosch) – and a line previously selected for low sternopleural bristle number for many generations from a Kaduna/Pacific source. In each of six replicate lines from each cross selection was practised for low sternopleural bristle number, and subsequently these replicates were intercrossed and reselected.Initially, similar responses were made in each set of lines, but subsequently more variation between replicates was found in Stellenbosch, which was the primary source of lines which responded to a level below that of the original selected line.It is concluded that this newly captured population contains genetic variability absent from the laboratory populations. Presumably variability has been lost from the latter populations, leaving essentially the same genes segregating in each.
Effects of gene dosage and hormones on the expression of Dr in the platyfish,Xiphophorus maculatus(Poeciliidae)
Authors: Valenti Robert J. , Kallman Klaus D. 
Published: September 2009

SUMMARYPlatyfish,Xiphophorus maculatus, are polymorphic for the patterns red-dorsal (Dr) and spotted-dorsal (Sd) fins, both controlled by closely linked loci on theXchromosome of Jamapa strain, Jp 163A. The intensity of red pigment looks the same in males and females, but spectrophotometric analysis of dorsal fin extracts showed that heterozygous intact males have significantly more red pigment (drosopterin) than homozygous or heterozygous females or castrated males. The mechanism of Dr expression in Jamapa is, thus, similar to the one present in the Belize stock, where a sex difference is readily apparent that is known to be under androgenic control. The Sd phenotype is identical in both sexes.SdandDrare not restricted to theXchromosome, and no evidence for gene dosage compensation has been obtained. Within the Jamapa stock the expression of Sd and Dr are best described in terms of dominance and recessiveness. Dr is strongly augmented by a testicular hormone.DrandSdhave been separated by crossing-over. In natural populations both genes can occur by themselves, linked to each other or to other pigment genes. The development of the Sd macromelanophores is not contingent upon the presence of pterinophores (Dr) in the dorsal fin or elsewhere in the body.
Genetic control of recombination inSchizophyllum commune: evidence for a new type of regulatory site
Authors: Stamberg Judith , Koltin Y. 
Published: September 2009

SUMMARYTwo strains ofS. communecharacterized by different levels of high recombination frequency in a particular region of the genome (between the two subunits, α and β, of theBincompatibility factor) were crossed, and their progeny tested for recombination frequency in the same region. The difference between the strains in recombination frequency is found to be due to some factor located within the recombining region itself.The segregation among the progeny indicates that the factor consists of a number of sites, with additive effects. This and the dominance relationships suggest that these sites may be recognition sites which comprise a part of the fine control of recombination.
An incompatibility system determined by three factors in a species of Psathyrella (Basidiomycetes)
Authors: Jurand M. K. , Kemp R. F. O. 
Published: September 2009

SUMMARYEvidence is given for a trifactorial system of incompatibility in an isolate identified as Psathyrella coprobia. The three factors are designated A, B and C. They are thought to be inherited independently. The function of factor A is most probably the same as that of factor A of bifactorial species. Factor B is concerned with the initiation of fruit body primordia, while all three factors must be heterozygous for the occurrence of nucleár migration and the formation of mature fruit bodies.
Genetic control of the kinetics of mouse spermatogenesis
Authors: Bruce W. Robert , Furrer Rudolf , Goldberg Robert B. , Meistrich Marvin L. , Mintz Beatrice 
Published: September 2009

SUMMARYThe kinetics of spermatogenesis in the mouse, and the possible genetic controls, have been investigated in different genotypes by means of the method of velocity sedimentation at unit gravity to separate testis cells and nuclei labelled with tritiated thymidine. The progression of the radioactivity through different sedimentation classes of cells provides a measure of their kinetics. The results demonstrate kinetic differences at the stage of spermatocyte differentiation between the C57BL/6 and AKR inbred strains of Mus musculus musculus and in randombred mice of the subspecies Mus m. molossinus. These kinetic differences are controlled by genetic factors which are not linked to the Y chromosome. The relevant autosomal alleles of C57BL/6 are dominant over those of AKR in F1 hybrids.
Definition of the blue mutant phenotype and its genetic basis inSaccharomyces cerevisiae
Authors: de G. Mitchell I. , Bevan E. A. 
Published: September 2009

SUMMARYMutant colonies of yeast are described which varied in colour from blue to green and in intensity of colour when grown on medium containing methylene blue. Blue mutant colonies contained more dead cells, decolorized redox dyes more slowly, had a higher respiratory quotient on glucose containing medium, and absorbed more methylene blue dye than did wild-type. The blue colony phenotype was induced both spontaneously and at high frequency by ultraviolet light and ethylmethane-sulphonate in both haploid and diploid strains. Many of the light-coloured colonies isolated following mutagenic treatment reverted to wild-type when subcultured but most dark-coloured colonies remained stable. Stable blue mutants were shown to arise by mutation of many separate nuclear genes in haploids and were often caused by recessive lethals in diploids.
Variation in the basal level of alkaline phosphatase inCoprinus lagopuswild-type strains
Authors: North Jane , Lewis D. 
Published: September 2009

SUMMARYTwo wild-type strains ofCoprinus lagopusisolated from a single basidiocarp differ by a factor of two in their basal level of alkaline phosphatase. The gene responsible for this difference is allelic toreg-2and unlinked to thepholoci; the allele conferring a lower basal level is dominant both in diploids and dikaryons.
The three locus model with multiplicative fitness values
Authors: Strobeck Curtis 
Published: September 2009

SUMMARYThe necessary and sufficient conditions for the stability of the equilibrium point with no linkage disequilibrium are obtained for the three locus model with multiplicative fitnesses. It is shown that there are six inequalities that must be satisfied in order for this equilibrium to be stable. Three of the inequalities require that there be heterozygotic superiority at all loci. The other three are exactly those inequalities which are required for each pair of loci to be stable with linkage equilibrium if they are considered to be an isolated two locus system. Thus, all the information needed to determine the stability of this equilibrium with three loci is contained in one and two locus theory.