DNA replication is said to be semiconservative because: One of the new molecules conserves both of the original DNA strands. The new DNA molecule contains two new DNA strands. Both of the new molecules contain one new strand and one old strand. DNA polymerase conserves both of the old strands.
The Correct Answer and Explanation is:
The correct answer is: Both of the new molecules contain one new strand and one old strand.
DNA replication is described as semiconservative because, during the replication process, each of the two new DNA molecules formed contains one original (parental) strand and one newly synthesized strand. This method contrasts with other possible replication mechanisms, such as conservative replication, where both strands of the new DNA molecule would be entirely new, or dispersive replication, where both strands would be a mix of old and new sections.
Here’s how the semiconservative mechanism works:
- Initiation: DNA replication begins when the double helix is unwound by helicase, creating two single-stranded DNA templates. These strands serve as templates for the synthesis of new complementary strands.
- Elongation: DNA polymerase reads the template strands and synthesizes new complementary strands by adding nucleotides that match the exposed bases on each parent strand (adenine to thymine, cytosine to guanine).
- Result: After the replication process, each of the two new double-stranded DNA molecules consists of one strand that is from the original DNA (old strand) and one strand that is newly synthesized (new strand).
This semiconservative model was first confirmed by the famous experiment conducted by Matthew Meselson and Franklin Stahl in 1958. They used nitrogen isotopes to label the DNA in E. coli and observed the pattern of DNA density after several rounds of replication. The results clearly showed that after one round of replication, each DNA molecule consisted of one heavy (old) strand and one light (new) strand, supporting the semiconservative theory.
This mechanism ensures that the genetic information is faithfully passed on with minimal errors, maintaining the integrity of the DNA sequence through generations.
