In the late 1950s, Meselson and Stahl grew bacteria in a medium containing "heavy"
(radioactive) nitrogen (15N) and then transferred them to a medium containing 14N, which is a
less radioactive form of nitrogen. They then extracted DNA from the bacteria and centrifuged it
to separate the DNA of different densities. Once the pattern found after one round of replication
was observed, Meselson and Stahl could be confident of which of the following conclusions?
A) Replication is semiconservative.
B) Replication is not dispersive.
C) Replication is not semiconservative.
D) Replication is not conservative.
