What does the polymerase chain reaction allow scientist do?

Answer 1

This powerful technique offers a faster and more convenient method of amplifying a specific DNA segment of up to 6 kb (kilobases). In this technique, a denatured (strand-separated) DNA sample is incubated with DNA polymerase, dNTPs (deoxynucleoside triphosphates), and two oligonucleotide primers whose sequence flank the DNA segment of interest so that they direct the DNA polymerase to synthesize new complementary strands. Multiple cycles of this process, each doubling the amount of DNA present, geometrically amplify the DNA starting from as little as a single gene copy. In each cycle, the two strands of the duplex DNA are separated by heat denaturation, the primers are annealed to their complementary segments on the DNA, and the DNA polymerase directs the synthesis of the complementary strands. Twenty cycles of PCR amplification increase the amount of the target sequence around one-millionfold with high specificity.

PCR amplification has become an indispensable tool in a great variety of applications. Clinically, it is used for the rapid diagnosis of Infectious Diseases and the detection of rare pathological events such as mutations leading to cancer. Forensically, the DNA from a single hair or sperm can be used to identify the donor unambigously. Moreover, PCR is also largely responsible for the newly emerging science of molcular Paleontology, thus, DNA that was extracted from a 120 to 135 million year old amber-entombed weevil was sufficiently preserved to permit amplification by PCR and subsequent sequencing.