Question

PCR (polymerase chain reaction) is an excellent method of generating copies of target DNA. If a single piece of double stranded DNA (dsDNA) is put into a PCR machine, how many dsDNA segments will there be after 3 rounds?

Answer 1

Answer: After 3 rounds, 8 segments having 2 original strands on different segments will be present.

Explanation:

The polymerase chain reaction selectively and repeatedly copy the double stranded DNA (dsDNA) in the PCR machine.

1st round:

Single piece of double stranded DNA (dsDNA) unwinds in two seperate strands, before complementary nucleotides are synthesized to establish double helix.

2nd round:

The two dsDNA yields 4 segments before complementary nucleotides are synthesized

3rd round:

The four dsDNA yields 8 segments before complementary nucleotides are synthesized.

Therefore, at the end of 3 rounds, the two original strands will be present on the 8 different segments of copied DNA.