Which phase is the synthesis phase of the cell cycle in which DNA is replicated?

Which phase is the synthesis phase of the cell cycle in which DNA is replicated?

• A. Gap 1 (G1)
• B. S phase (synthesis)
• C. Gap 2 (G2)
• D. M phase (mitosis)

Answer: (B)

DNA replication happens during the S phase, the synthesis stage of the cell cycle. In this phase, each chromosome is duplicated so that two sister chromatids form and stay attached at the centromere. This doubles the cell’s DNA content, setting the stage for equal distribution of genetic material when the cell enters division. The other phases are growth and preparation (G1), a second growth and checkpoint period after replication (G2), and the division stage (M) where mitosis and cytokinesis occur. Replication must occur before division, so the S phase is the key time when DNA is synthesized.

DNA replication happens during the S phase, the synthesis stage of the cell cycle. In this phase, each chromosome is duplicated so that two sister chromatids form and stay attached at the centromere. This doubles the cell’s DNA content, setting the stage for equal distribution of genetic material when the cell enters division. The other phases are growth and preparation (G1), a second growth and checkpoint period after replication (G2), and the division stage (M) where mitosis and cytokinesis occur. Replication must occur before division, so the S phase is the key time when DNA is synthesized.