Question

While conducting experiments with E. coli, Meselson and Stahl established that during DNA replication, each of the two strands of the double helix serves as the template for the new strand of DNA. Scientists describe this process as semiconservative. What does "semiconservative" mean in terms of DNA replication?

a) Both original DNA strands are completely conserved in the new DNA.
b) One original DNA strand is conserved, and the other is completely replaced in the new DNA.
c) Both original DNA strands are completely replaced in the new DNA.
d) One original DNA strand is conserved, and the other is partially replaced in the new DNA.

Answer 1

The term "semiconservative" refers to when b) one original DNA strand is conserved, and the other is completely replaced in the new DNA.

Step-by-step explanation:

The term "semiconservative" in terms of DNA replication means that each of the two strands of DNA serves as a template for the new strand, resulting in two double-stranded DNA molecules, each composed of one original "parental" strand and one new "daughter" strand. Therefore, after replication, each new DNA molecule conserves half of the original DNA molecule, hence the term semiconservative.

This was demonstrated by the Meselson-Stahl experiment which confirmed that DNA replication does not involve the original strands being completely conserved (option a), completely replaced (option c), or one being partially replaced (option d). Instead, it follows option b: One original DNA strand is conserved, and the other is completely replaced in the new DNA.