ABSTRACT
The toolkit of techniques used by molecular biologists to study DNA molecules was assembled during the 1970s and 1980s. The development of more direct methods for studying DNA was stimulated by breakthroughs in biochemical research that, in the early 1970s, provided molecular biologists with enzymes that could be used to manipulate DNA molecules in the test tube. Recombinant DNA methodology led to development of the polymerase chain reaction (PCR). An important feature of template-dependent DNA synthesis is that a DNA polymerase is unable to use an entirely single-stranded molecule as the template. Two types of gel are used in molecular biology: agarose gels and polyacrylamide gels, which are mainly used in DNA sequencing. PCR results in the repeated copying of a selected region of a DNA molecule. DNA cloning was the first of the important new research tools that were developed during the early years of the recombinant DNA revolution.
