Question

In PCR (Polymerase Chain Reaction), the annealing temperature must be ______ enough for primers to bind to the strand but ______ enough for this binding to be specific (bind in the correct place).

a) High, low
b) Low, high
c) Moderate, moderate
d) Variable, constant

Answer 1

In PCR, the annealing temperature needs to be low enough to permit primer binding but high enough to ensure that this binding is specific.

Step-by-step explanation:

In PCR (Polymerase Chain Reaction), the annealing temperature must be low enough for primers to bind to the strand but high enough for this binding to be specific (bind in the correct place).

During PCR, after denaturation at high temperatures (usually around 94°C to 95°C), the temperature must be lowered for the primer annealing step. However, this temperature needs to be carefully controlled: it must not be too low, or primers may bind non-specifically, and not too high, or they may not bind at all. Annealing generally occurs at about 5°C below the melting temperature of the primer, which is often in the range of 50°C to 65°C. Therefore, the accurate balance of the annealing temperature is critical for specificity and efficient amplification.