DNA replication is said to be
A) nonconservative
B) liberal
C) exclusive
D) conservative
E) semiconservative
F) inconclusive
The correct answer and explanation is:
The correct answer is E) semiconservative.
DNA replication is described as semiconservative because, during the process of replication, each of the two strands of the original DNA molecule serves as a template for the formation of a new complementary strand. After replication, the resulting DNA molecules each consist of one strand from the original (parent) molecule and one newly synthesized strand.
This concept was first demonstrated in an experiment by Matthew Meselson and Franklin Stahl in 1958. They used isotopes of nitrogen to distinguish between the old and new DNA strands. By using heavy nitrogen (N-15) and light nitrogen (N-14), they were able to track the newly synthesized DNA. After one round of replication, they observed that the DNA had an intermediate density, showing that each new DNA molecule consisted of one old strand and one new strand. This result confirmed that DNA replication is semiconservative.
The semiconservative nature of DNA replication is critical for maintaining genetic stability. If replication were conservative (option D), the parent DNA molecule would remain intact, and the new DNA molecule would consist entirely of newly synthesized strands. Alternatively, if replication were nonconservative (option A), the parent DNA would be discarded entirely, and both strands of the new DNA molecule would be synthesized from scratch, which would be a less efficient method of replication.
The semiconservative model ensures that genetic information is accurately passed on from one generation to the next, allowing for continuity of genetic traits while also introducing variability in the form of mutations during the replication process, which is crucial for evolution.