Question

Given below are two statements.

Statement I - In Meselson and Stahl's experiment the samples were separated by using CsCl equilibrium gradients.

Statement II - \({ }^{15} \mathrm{~N}\) is a heavy isotope and can be separated based on density gradient.

In the light of above statements, select the correct option given below:

• A. Both statement I and statement II are correct.
• B. Both statement I and statement II are incorrect.
• C. Statement I is correct but statement II is incorrect.
• D. Statement I is incorrect but statement II is correct.

Hint:

Recall the heavy isotope and the centrifugation method used in this experiment.

Answer 1

The Correct Option is A

Step 1: Understanding the Concept
Meselson and Stahl showed that DNA replicates semi-conservatively.

Step 2: Check Statement I
They separated the DNA samples by equilibrium density gradient centrifugation in CsCl, so it is correct.

Step 3: Check Statement II
\(^{15}\text{N}\) is a heavy isotope of nitrogen, so DNA containing it is denser and can be separated on a density gradient. This is correct.

Step 4: Conclusion
Both statements are correct.

Final Answer:
Both statements are correct. \[ \boxed{\text{(A) }\text{Both statement I and statement II are correct.}} \]