Question

In PCR, the temperature must be _____ from the denaturation temperature in order for primers to anneal.

a) Higher
b) Lower
c) Same
d) Irrelevant

Answer 1

In PCR, the temperature must be lower than the denaturation temperature to enable primer annealing, typically around 55 ºC for efficient primer-DNA binding.

Step-by-step explanation:

In PCR, the temperature must be lower from the denaturation temperature in order for primers to anneal. When preparing for the annealing step in PCR, the temperature is generally reduced to approximately 55 ºC, which is typically 5 ºC below the primer's melting temperature, to allow the primers to form Watson-Crick base pairs with the DNA. This is crucial because a too high annealing temperature, like 65 ºC instead of the intended 50 ºC, can prevent primers from annealing effectively, leading to a failed or inefficient PCR reaction. Therefore, the correct option is (b) Lower.