Читать книгу Snyder and Champness Molecular Genetics of Bacteria - Tina M. Henkin - Страница 44

The early 1960s saw the start of the discovery of many interesting and useful bacterial and phage enzymes involved in DNA and RNA metabolism. In 1960, Arthur Kornberg demonstrated the synthesis of DNA in the test tube by an enzyme from E. coli. The next year, a number of groups independently demonstrated the synthesis of RNA in the test tube by RNA polymerases from bacteria. From that time on, other useful enzymes for molecular biology were isolated from bacteria and their phages, including additional RNA and DNA polymerases, polynucleotide kinase, DNA ligases, topoisomerases, and many phosphatases.

From these early observations, the knowledge and techniques of molecular genetics exploded. For example, in the early 1960s, techniques were developed for detecting the hybridization of RNA to DNA and DNA to DNA on nitrocellulose filters. These techniques were used to show that RNA is made on only one strand in specific regions of DNA, which later led to the discovery of promoters and other regulatory sequences. By the late 1960s, restriction endonucleases had been discovered in bacteria and shown to cut DNA in specific places (see Linn and Arber, Suggested Reading). By the early 1970s, these restriction endonucleases were being exploited to introduce foreign genes into E. coli (see Cohen et al., Suggested Reading), and by the late 1970s, the first human gene had been expressed in a bacterium. Also in the late 1970s, methods to sequence DNA by using enzymes from phages and bacteria were developed.

In 1988, a thermally stable DNA polymerase from a thermophilic bacterium was used to invent the technique called the polymerase chain reaction (PCR). This extremely sensitive technique allows the amplification of genes and other regions of DNA, facilitating their cloning and study. Thermally stable DNA polymerases are now an essential tool for genome sequencing.