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?

a. 16 segments with the 2 original strands on different segments

b. 8 segments, with the 2 original strands paired

c. 16 segments, with the 2 original strands paired

d. 8 segments with the 2 original strands on different segments

Answer: Option D) 8 segments, with the 2 original strands on different segments

Explanation:

During polymerase chain reaction, a double stranded DNA (dsDNA) is selectively and repeatedly copied in the PCR machine.

In the first round, the single piece of double stranded DNA (dsDNA) unwinds in two seperate strands, before complementary nucleotides are synthesized to establish double helix.

In the second round, the two dsDNA yields 4 segments before complementary nucleotides are synthesized to establish double helix.

In the third round, the four dsDNA yields 8 segments before complementary nucleotides are synthesized to establish double helix.

Thus, after 3 rounds, the two original strands are on the 8 different segments of copied DNA.