Which phase of the cell cycle involves DNA synthesis?

Which phase of the cell cycle involves DNA synthesis?

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

Answer: (B)

DNA synthesis occurs during S phase, the stage where the genome is copied in preparation for cell division. During this part of interphase, the cell duplicates each chromosome so that there are two sister chromatids per chromosome, held together at the centromere. This doubling of DNA content is why S stands for synthesis. The other phases don’t involve replication: G1 is a growth and metabolic phase before DNA duplication, G2 is a final preparation and quality-check before division, and M phase is when the chromosomes are actually separated into two new cells.

DNA synthesis occurs during S phase, the stage where the genome is copied in preparation for cell division. During this part of interphase, the cell duplicates each chromosome so that there are two sister chromatids per chromosome, held together at the centromere. This doubling of DNA content is why S stands for synthesis. The other phases don’t involve replication: G1 is a growth and metabolic phase before DNA duplication, G2 is a final preparation and quality-check before division, and M phase is when the chromosomes are actually separated into two new cells.