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. S phase
• C. G2 phase
• D. M phase

Answer: (B)

DNA replication occurs during the S phase of the cell cycle. This phase is critical as it is specifically designated for the synthesis of new DNA, which results in the duplication of the genetic material within the cell. During S phase, each chromosome is replicated to form two sister chromatids, ensuring that each daughter cell will receive an identical set of chromosomes after cell division. Prior to the S phase, during the G1 phase, the cell is primarily focused on growth and preparation for DNA synthesis, but no actual replication occurs. Following the S phase, the G2 phase also does not involve DNA replication; instead, it is a period where the cell continues to grow, produces proteins, and prepares for mitosis. During the M phase, the cell undergoes mitosis and cytokinesis, stages in which the duplicated chromosomes are separated and distributed into the daughter cells, but again, no replication takes place during this time. Thus, S phase is the key phase where DNA replication is ensured and completed.

DNA replication occurs during the S phase of the cell cycle. This phase is critical as it is specifically designated for the synthesis of new DNA, which results in the duplication of the genetic material within the cell. During S phase, each chromosome is replicated to form two sister chromatids, ensuring that each daughter cell will receive an identical set of chromosomes after cell division.

Prior to the S phase, during the G1 phase, the cell is primarily focused on growth and preparation for DNA synthesis, but no actual replication occurs. Following the S phase, the G2 phase also does not involve DNA replication; instead, it is a period where the cell continues to grow, produces proteins, and prepares for mitosis. During the M phase, the cell undergoes mitosis and cytokinesis, stages in which the duplicated chromosomes are separated and distributed into the daughter cells, but again, no replication takes place during this time. Thus, S phase is the key phase where DNA replication is ensured and completed.