DNA synthesis takes place during which phase of the cell cycle________________?
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Answer: D. Synthesis – S phase
Explanation
Replication of cellular genetic material occurs exclusively during the S phase of the cell cycle. DNA synthesis ensures that daughter cells receive an exact duplicate of the genome during subsequent division. Accurate replication requires complex enzymatic machinery operating during this specific interphase period. The cell cycle consists of G1, S, G2, and M phases regulating orderly cellular division. Mitosis or M phase involves nuclear division and cytokinesis following successful DNA replication. Gap phases G1 and G2 allow cells to grow and prepare enzymatically for upcoming replication and division.
Many cancer chemotherapeutic agents target rapidly dividing cells by disrupting DNA synthesis during the S phase. Flow cytometry laboratories measure cellular DNA content to determine cell cycle phase distributions. Cell cycle checkpoints monitor DNA integrity during the S phase to prevent mutagenic replication errors. Option A is incorrect because mitosis involves chromosome segregation and cellular division rather than DNA synthesis. Option B is wrong since the G2 phase prepares the cell for mitosis after DNA synthesis is already complete. Option C is incorrect because the G1 phase precedes DNA synthesis and involves cellular growth and preparation.
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