Question

The correct depiction of the experiment performed by Matthew Meselson and Franklin Stahl to prove that DNA replicates semi-conservatively on separation of DNA by centrifugation after 40 minutes is:

• A.
• B.
• C.
• D.

Hint:

In semi-conservative DNA replication, the first generation after switching to \textsuperscript{14}N medium always shows a single intermediate band—half heavy, half light strands.

Answer 1

The Correct Option is C

Step 1: Meselson and Stahl used ¹⁵N (heavy nitrogen) to label the DNA in E. coli, which was then transferred to a ¹⁴N (light nitrogen) medium.
Step 2: After 40 minutes (approximately one generation), DNA was extracted and centrifuged.
Step 3: Semi-conservative replication means that each daughter DNA consists of one old (heavy) and one new (light) strand.
Step 4: This results in a single band of intermediate density in the centrifuge.