During which phase of the cell cycle does DNA replication occur?

During which phase of the cell cycle does DNA replication occur?

• A. G1 phase
• B. G2 phase
• C. M phase
• D. S phase

Answer: (D)

DNA replication happens during the S phase, the synthesis period of the cell cycle. In this phase, the cell copies its entire genome so each chromosome now has two sister chromatids that will be separated later during division, ensuring both daughter cells receive a full set of genetic information. The S phase sits between the growth-focused G1 phase and the preparation/maturation G2 phase, and it occurs before mitosis, which is the M phase where division actually happens. Since only the S phase is dedicated to duplicating the DNA, it’s the phase that best fits the question asking when replication occurs.

DNA replication happens during the S phase, the synthesis period of the cell cycle. In this phase, the cell copies its entire genome so each chromosome now has two sister chromatids that will be separated later during division, ensuring both daughter cells receive a full set of genetic information. The S phase sits between the growth-focused G1 phase and the preparation/maturation G2 phase, and it occurs before mitosis, which is the M phase where division actually happens. Since only the S phase is dedicated to duplicating the DNA, it’s the phase that best fits the question asking when replication occurs.