What is the typical range of temperature required for annealing in PCR?

The typical range of temperature required for annealing in PCR (Polymerase Chain Reaction) is indeed between 40°C and 65°C. During the annealing step, the temperature is optimized to allow the primers to bind to their complementary sequences on the DNA template. This temperature range is crucial because it allows for specific binding while preventing non-specific interactions that could lead to undesired amplification products.

At lower temperatures, like those in the 30°C - 40°C range, the primers may not bind effectively due to insufficient thermal energy, leading to poor specificity and efficiency in the reaction. Conversely, at higher temperatures (such as 65°C - 90°C), while some hybrids may form, there is a greater risk of the primers and template not binding together properly due to increased thermal instability. Extremely high temperatures (90°C - 100°C) would lead to the denaturation of the DNA and discourage primer annealing altogether.

Therefore, the chosen range strikes a balance that enhances the specificity of the primer annealing, facilitating successful DNA amplification during PCR.