Which step is NOT part of a standard PCR cycle?

Which step is NOT part of a standard PCR cycle?

• A. Denaturation
• B. Primer annealing
• C. Extension
• D. Ligare step

Answer: (D)

PCR amplifies DNA through cycles of denaturation, primer annealing, and DNA synthesis (extension). Denaturation uses heat to separate the double-stranded DNA; annealing allows primers to bind to complementary sequences; extension involves a DNA polymerase extending from the primers to synthesize new DNA strands. Ligation, which uses DNA ligase to join DNA fragments, is a separate reaction used in cloning or assembly workflows and does not occur during a standard PCR cycle. Therefore, ligation is the step that is not part of a standard PCR cycle.

PCR amplifies DNA through cycles of denaturation, primer annealing, and DNA synthesis (extension). Denaturation uses heat to separate the double-stranded DNA; annealing allows primers to bind to complementary sequences; extension involves a DNA polymerase extending from the primers to synthesize new DNA strands. Ligation, which uses DNA ligase to join DNA fragments, is a separate reaction used in cloning or assembly workflows and does not occur during a standard PCR cycle. Therefore, ligation is the step that is not part of a standard PCR cycle.