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 would you expect if the DNA was replicated in a conservative manner?
A) A
B) B
C) C
D) D

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 would you expect if the DNA was replicated in a conservative manner?
A) A 
B) B 
C) C 
D) D

Quizplus · Accepted Answer

If DNA replication occurred in a conservative manner, both daughter strands would have the parental (heavy) nucleotides, and there would be one "heavy" band and one "light" band after centrifugation. This corresponds to the pattern labeled B in the figure. Patterns A and C represent semi-conservative replication and pattern D represents dispersive replication.

A Space Probe Returns with a Culture of a Microorganism