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Question
An experiment is conducted in which proliferating cells are subjected to ionizing radiation. The ionizing radiation leads to arrest in a checkpoint that monitors completion of DNA replication. It is observed that there are increased numbers of chromosomal abnormalities in these cells.
Which of the following is the checkpoint affected by the ionizing radiation?
A G0/G1

B G1/S

C S/G2

D G2/M

E M/G0
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Answer / Explanation:

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(D) CORRECT.

This is the second checkpoint in the cell cycle; ionizing radiation activates this checkpoint, resulting in chromosomal abnormalities in mitosis.
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