In PCR, during extension, what occurs?

In PCR, during extension, what occurs?

• A. one to several mins at 50-65 C
• B. no polymerase activity occurs
• C. higher temp, DNA polymerase extends and synthesizes complementary DNA strand to each primer
• D. lower temp, primers dissociate

Answer: (C)

During extension the polymerase works at its optimal higher temperature (about 72°C for Taq polymerase). It binds to the primers and adds nucleotides to the 3' ends, synthesizing the complementary DNA strand on each template. This is the step that builds the new strands and completes the amplification cycle. The other statements mix up the roles: annealing occurs at lower temperatures to allow primers to bind, and polymerase activity is essential during extension, not absent. extension is not performed at 50-65°C in the way those words describe.

During extension the polymerase works at its optimal higher temperature (about 72°C for Taq polymerase). It binds to the primers and adds nucleotides to the 3' ends, synthesizing the complementary DNA strand on each template. This is the step that builds the new strands and completes the amplification cycle. The other statements mix up the roles: annealing occurs at lower temperatures to allow primers to bind, and polymerase activity is essential during extension, not absent. extension is not performed at 50-65°C in the way those words describe.