Multiple choice

E.coli bacteria are placed in a medium, which is inoculated with radioactive guanosine for 5 minutes. Then it was made to replicate in a normal medium. Which of the following is correct for the replication process of DNA?

  1. Each strand will be partly radioactive.

  2. Both the strands of DNA are radioactive.

  3. Only one strand will be radioactive.

  4. Radioactivity is seen only on the leading strand.

  5. None of the strands is radioactive.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Only one strand will be radioactive. Replication of DNA is semi-conservative in nature. Hence, a new strand is formed on the template DNA strand. The new strand while replicating use radioactive guanosine from the medium but the template strand would not have the radioactive G. Therefore after 5 minutes, only one strand, i.e. the newly produced strand will have the radioactive guanosine.

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