Question

Which of the following is in the correct order for one cycle of polymerase chain reaction (PCR)?

A. Extend primers; anneal primers; denature DNA.
B. Anneal primers; denature DNA extend primers.
C. Denature DNA anneal primers; extend primers.
D. Denature DNA; add fresh enzyme; anneal primers, add dNTPs; extend primers.

Answer 1

The correct order for a cycle of PCR is: denaturing the DNA, annealing primers to the single strands, and then extending the primers with Taq polymerase.

Step-by-step explanation:

The correct order for one cycle of Polymerase Chain Reaction (PCR) is represented by option C: Denature DNA, anneal primers, extend primers.

During the PCR process, the following steps occur:

1. Denaturing entails heating the double-stranded DNA to around 95°C to separate the strands into single strands.
2. Annealing then takes place when the temperature is lowered to about 50-65°C, allowing primers that match the target sequence to bind or anneal to the single-stranded DNA.
3. Finally, Extension occurs at a temperature of around 72°C where Taq polymerase synthesizes a new strand of DNA by adding nucleotides to the primers.

This cycle is usually repeated 25-40 times to exponentially amplify the DNA segment of interest.