Q: Explain the functions of primers in PCR

Primers mark out a sequence of DNA to amplify. This sequence would be complementary to the target DNA strand which it attaches itself to. They also prevent the single stranded DNA from re-annealling by sticking to a part of the target DNA. They also allow Taq polymerase to work from a 5' to 3' direction, since the enzyme can only work with a free 3' end.