Question

A bacterium with completely radioactive DNA was allowed to replicate in a non-radioactive medium for two generation, what % of the bacteria should contain radioactive DNA?

• A. 100 %
• B. 50 %
• C. 25 %
• D. 12.5 %

Answer 1

Answer: (B)

50 %

A bacterium, with completely radioactive DNA, was allowed to replicate in a non-radioactive medium for two generation, the percentage of the bacteria which should contain radioactive DNA will be 50% because the mode of DNA replication is semi-conservative, which leads to the production of two DNA molecules with the radioactive strand. After the second duplication, the two molecules of DNA out of four contains radioactive strand.

So, the percentage of radioactive DNA will be 50%.

So, the correct answer is option B.