-A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in ¹⁵N medium for several generations and then transfer them to ¹⁴N medium. Which pattern in the figure above would you expect if the DNA was replicated in a conservative manner?
A) A
B) B
C) C
D) D
E) E

Question

-A space probe returns with a culture of a microorganism found on a distant planet. Analysis shows that it is a carbon-based life-form that has DNA. You grow the cells in ¹⁵N medium for several generations and then transfer them to ¹⁴N medium. Which pattern in the figure above would you expect if the DNA was replicated in a conservative manner?
A) A 
B) B 
C) C 
D) D 
E) E

Quizplus · Accepted Answer

In conservative replication, the original DNA molecule is conserved, and a completely new molecule is synthesized. After switching from ¹⁵N to ¹⁴N medium, one would expect to see one band of heavy DNA (¹⁵N) and one band of light DNA (¹⁴N) after the first replication, which matches the pattern described in option B.

-A Space Probe Returns with a Culture of a Microorganism