Typically 2030 base primers for PCR are used for amplificati

Typically 20-30 base primers for PCR are used for amplification. Why do you think this is true?

Solution

The primer should only bind to a perfectly complementary part of the template. It should not bind to random sites. Stable DNA–DNA hydrogen bonds are only formed when the primer sequence very closely matches the template sequence. Since the mammalian DNA contains 3 billion base pairs, if we take a primer with 20-30 base pairs, the chances o f the primer binding to the target DNA at random site greatly decreases. At least the primer must be 20 base pairs long to make random matches unlikely.