Like Eckloff, many researchers have apparently abandoned this time-consuming procedure, which also involves the use of hazardous chemicals. That's not to say that molecular biologists have single-mindedly embraced kits, however. Care has to be taken to avoid slipping into a quick and easy way of doing science under the guise of saving time, especially with the heavy pressure to produce results more quickly than the competitors. For these clients, suppliers have developed systems for the extraction and purification of genomic DNA for PCR templates and the purification of synthetic oligonucleotide primers. They have also developed cleanup protocols for PCR products prior to further manipulation.
Some suppliers offer kits to extract and purify genomic DNA from specific sources.
It includes grinding spheres, which are vortexed with frozen plant tissue to break open tough cell walls. Gentra Systems' Generation DNA Purification System for rapid purification of genomic DNA from tissues or fluids. The other DNA component for PCR, oligonucleotide primers, must also be purified after they are automatically synthesized. For most PCR primers, which are typically shorter than 30 bases in length, simple desalting through gel filtration columns like those sold by Pharmacia Biotech Inc. of Piscataway, N.J., is usually sufficient, he says. Following PCR, amplified DNA must be purified away from unincorporated primers and other reaction components.