(i) Mention the number of primers required in each cycle of polymerase chain reaction
(PCR). Write the role of primers and DNA polymerase in PCR.
(ii) Give the characteristic feature and source organism of the DNA polymerase used
(i) 1. There are two sets of primers required in PCR usually 10-18 nucleotide
long and complementary to sequences present at 3' of the target DNA segment.
2. The primers are used during annealing for the addition of nucleotide for
making of multiple copies of the DNA of interest.
3. The enzyme DNA polymerase synthesizes DNA segment between the primers.
(ii) Characteristic feature :
1. The characteristic feature of PCR is that multiple copies of the desired
gene are synthesized in vitro.
2. It involves three steps: Denaturation, Annealing and Extension.
3. Taq polymerase is used, which is obtained from Thermus aquaticus. It is
thermostable and can withstand the high temperature used in the denaturation process.