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Question
Escherichia coli is allowed to replicate once in medium having radioactive thymidine. Which one is correct?
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Solution
The correct option is C One strand becomes radioactive.
DNA replication is semiconservative in which a DNA strand serves as a template for the synthesis of a new strand and produces two new DNA molecules, each with one new strand and one parental strand. The culture of E. coli in radioactive thymidine incorporates tritium in place of the hydrogen atom in thymidine. DNA replication in tritiated thymidine medium synthesizes daughter DNA strand with tritiated thymidine; the new DNA duplex is hybrid of daughter strand with tritiated thymidine and parental DNA strand with normal thymidine; option B is correct. DNA isolated just before replication shows no radioactivity; option D is incorrect. The second round of cell division produces 50% DNA with both radioactive strands and 50% DNA intermediate DNA; option A is incorrect. DNA replication is not dispersive which rule out option C.
DNA replication is semiconservative in which a DNA strand serves as a template for the synthesis of a new strand and produces two new DNA molecules, each with one new strand and one parental strand. The culture of E. coli in radioactive thymidine incorporates tritium in place of the hydrogen atom in thymidine. DNA replication in tritiated thymidine medium synthesizes daughter DNA strand with tritiated thymidine; the new DNA duplex is hybrid of daughter strand with tritiated thymidine and parental DNA strand with normal thymidine; option B is correct. DNA isolated just before replication shows no radioactivity; option D is incorrect. The second round of cell division produces 50% DNA with both radioactive strands and 50% DNA intermediate DNA; option A is incorrect. DNA replication is not dispersive which rule out option C.
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