As additional evidence that U238 has an unusual mode of DNA replication, you conduct still another Meselson-Stahl type experiment, again allowing the virus to replicate in the presence of "heavy" nitrogen until both strands of its genome are "heavy." This time you allow U238 to undergo three complete rounds of replication in the presence of "light" nitrogen. What ratio of "heavy" to "light" viral DNA would you expect to find after three complete rounds of replication?
A)1:7
B)2:6
C)4:4
D)6:2
E)7:1

Question

Quizplus · Accepted Answer

After three rounds of replication starting with heavy DNA, the distribution of heavy to light DNA would follow a pattern where in each round, the amount of light DNA doubles while the heavy DNA remains constant or decreases. After three rounds, there would be one part heavy to seven parts light DNA, assuming each round of replication halves the amount of heavy DNA and doubles the amount of light DNA.

As Additional Evidence That U238 Has an Unusual Mode of DNA