A student tries to repeat Meselson-Stahl’ experiment but forgot to label the med
ID: 51586 • Letter: A
Question
A student tries to repeat Meselson-Stahl’ experiment but forgot to label the medium with which radioactive probe is used (15N or 14N). The density profiles of the DNA molecules are as follows:
Before DNA replication
After 1 generation
After 2 generations
One heavy band
One medium band
One light band and one medium band
Can you infer which medium he has used?
He started with 14N, then transferred to 15N.
He started with 14N, then transferred to 15N, then back to 14N.
He started with 15N, then transferred to 14N.
He started with 15N, then transferred to 14N, then back to 15N.
Before DNA replication
After 1 generation
After 2 generations
One heavy band
One medium band
One light band and one medium band
Explanation / Answer
Thge student started Meselson - Stahl experiment with medium 15N since density profile had shown one heavy band prior replication. Then he transferred to medium containing 14N and then back to 15N since, the density profiles after 1st and 2nd generation exhibit light, light and medium bands respectively. Hence, option D is correct.
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