During PCR, primers bind to the DNA strands in the step.
- ligation
- denaturation
- extension
- annealing
Answer
(4) annealing
Solution
In Polymerase Chain Reaction (PCR), each cycle consists of three steps:
1. Denaturation: The double-stranded DNA is separated into single strands at high temperature ( 94 C).
2. Annealing: Two sets of primers bind (anneal) to their complementary sequences on the single-stranded DNA templates at a lower temperature ( 50--60 C).
3. Extension: Thermostable Taq DNA polymerase extends the primers by adding nucleotides.
Thus, primers bind to the DNA strands in the annealing step.
Answer: (4)