Question

DNA replication is

• A. Conservative
• B. Dispersive
• C. Semi-conservative
• D. None of these

Hint:

The Meselson-Stahl experiment using heavy nitrogen ($^{15}N$) provided definitive evidence for semi-conservative DNA replication. Understanding this experiment helps solidify the concept.

Answer 1

The Correct Option is C

Step 1: Understanding the Question:
The question asks to describe the mechanism by which DNA replicates, specifically referring to how the new DNA molecules are composed of original and newly synthesized strands.

Step 3: Detailed Explanation:
- Semi-conservative replication: This is the established mechanism of DNA replication. During replication, the two strands of the parent DNA molecule separate. Each original strand then serves as a template for the synthesis of a new complementary strand. The result is two new DNA molecules, each consisting of one original (parental) strand and one newly synthesized strand. This mechanism was famously demonstrated by the Meselson-Stahl experiment.
- Conservative replication: In this hypothetical model, the parent DNA molecule would remain entirely intact, and a completely new daughter DNA molecule would be synthesized.
- Dispersive replication: In this hypothetical model, both original and newly synthesized DNA would be interspersed in both daughter molecules.
Therefore, the semi-conservative model is the correct description.

Step 4: Final Answer:
DNA replication is semi-conservative.