Question

Once DNA sequences have been amplified in PCR, what is the next step?

1) Denaturation
2) Annealing
3) Extension
4) All of the above

Answer 1

After DNA amplification in PCR, the next step in a single cycle is extension. However, all steps are repeated in subsequent cycles starting with denaturation.

Step-by-step explanation:

Once DNA sequences have been amplified in PCR, the next step that follows immediately within a single cycle of PCR is extension. However, if referring to the subsequent cycles in PCR following amplification, all of the aforementioned steps (denaturation, annealing, and extension) would be correct because the cycle starts again with denaturation.

PCR Cycle Steps

Denaturation: The double-stranded DNA is heated to break the hydrogen bonds between the strands, yielding single-stranded DNA.

Annealing: When the temperature is lowered, primers bind to the complementary sequences of the single-stranded DNA.

Extension: DNA polymerase extends the primers to form a new strand of DNA by adding nucleotides.

These steps are repeated through multiple cycles in a PCR machine, using temperatures specifically set for each stage to facilitate denaturation, annealing, and extension in sequence.