Question

Which of the following places the steps in the PCR procedure in the correct order?

1) Incubate at 94°C to denature DNA strands;
2) Incubate at 72°C for DNA synthesis;
3) Incubate at 60°C for primer hybridization.

1, 2, 3
1, 3, 2
2; 1; 3
3, 2, 1
3; 1; 2

Answer 1

The correct order for the PCR steps is denaturation at 94°C, annealing (primer hybridization) at around 60°C, and then extension (DNA synthesis) at 72°C, which corresponds to order 1, 3, 2.

Step-by-step explanation:

The correct order of steps in the Polymerase Chain Reaction (PCR) procedure is:

1. Incubate at 94°C to denature DNA strands.
2. Incubate at 60°C for primer hybridization.
3. Incubate at 72°C for DNA synthesis.

Therefore, the correct sequence is 1, 3, 2. Each of these steps requires a different temperature. The first step is denaturation, which involves heating the double-stranded DNA to around 94°C. The second step is annealing, where the temperature is lowered to approximately 55°C (though it may vary slightly) to allow the primers to attach to the template DNA. The final step is extension, which occurs at around 72°C, the optimal temperature for Taq polymerase to synthesize the new DNA strand.