Question:
The equilibrium sedimentation experiments performed by Meselson and Stahl in 1957 demonstrated that
The equilibrium sedimentation experiments performed by Meselson and Stahl in 1957 demonstrated that
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• Meselson–Stahl → Semiconservative replication
• Key idea: One old strand + One new strand
Updated On: May 13, 2026
- DNA replication takes place in a semiconservative fashion
- DNA is double stranded
- DNA chains are antiparallel
- The nucleotides in DNA contain sugar
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The Correct Option is A
Solution and Explanation
Concept:
The Meselson–Stahl experiment (1957) used isotopic labeling and density gradient centrifugation to determine the mechanism of DNA replication.
• Used \(^ {15}\text{N}\) (heavy nitrogen) and \(^ {14}\text{N}\) (light nitrogen)
• Demonstrated how DNA strands separate and replicate
Step 1: Understanding the experiment.
• After one generation → Hybrid DNA (one old + one new strand)
• After subsequent generations → Mix of hybrid and light DNA
Step 2: Conclusion from results.
This pattern supports semiconservative replication, where:
• Each daughter DNA molecule contains one parental strand and one newly synthesized strand
Step 3: Analyzing options.
• (A): Correct — Proven by Meselson–Stahl experiment.
• (B), (C), (D): Known from Watson-Crick model, not from this experiment.
Step 4: Selecting the correct answer.
Thus, the experiment demonstrated semiconservative replication.
• Used \(^ {15}\text{N}\) (heavy nitrogen) and \(^ {14}\text{N}\) (light nitrogen)
• Demonstrated how DNA strands separate and replicate
Step 1: Understanding the experiment.
• After one generation → Hybrid DNA (one old + one new strand)
• After subsequent generations → Mix of hybrid and light DNA
Step 2: Conclusion from results.
This pattern supports semiconservative replication, where:
• Each daughter DNA molecule contains one parental strand and one newly synthesized strand
Step 3: Analyzing options.
• (A): Correct — Proven by Meselson–Stahl experiment.
• (B), (C), (D): Known from Watson-Crick model, not from this experiment.
Step 4: Selecting the correct answer.
Thus, the experiment demonstrated semiconservative replication.
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