Matthew Meselson and Franklin Stahl demonstrated that DNA replication is semicon
ID: 206489 • Letter: M
Question
Matthew Meselson and Franklin Stahl demonstrated that DNA replication is semiconservative in bacteria.
What were the results of their experiment for two DNA replication cycles?
A) After one round of replication all of the DNA was 14N/15N; after two rounds half the DNA was 14N/15N and half was 14N/14N. B) After one round of replication all of the DNA was 14N/15N; after two rounds half the DNA was 14N/15N and half was 15N/15N. C) After one round of replication all of the DNA was 14N/14N; after two rounds half the DNA was 14N/15N and half was 15N/15N. D) After one round of replication all of the DNA was 14N/15N; after two rounds all of the DNA was 14N/14N. E) After one round of replication all of the DNA was 14N/14N; after two rounds all of the DNA was 15N/15N. F) After one round of replication all of the DNA was 14N/15N; after two rounds one third of the DNA was 14N/15N, one third was 14N/14N and one third was 15N/15N.Explanation / Answer
The answer is
Beacuse Meselson and Stahl first grown the bacteria in N15 media later transferred it in to N14 media. As the DNA replication occurs in semi conservative mode which means each daguther DNA molecule contains one new and one old DNA molecules, after first round the total DNA has N14/N15. After the second around, N14 stand will get another N14 strand and N15 strand will get another N14 strand. So, the answer is A.
A) After one round of replication all of the DNA was 14N/15N; after two rounds half the DNA was 14N/15N and half was 14N/14N.