During which phase of the cell cycle are chromosomes duplicated?

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

Answer: (D)

Verified step by step guidance

1. Understand the cell cycle: The cell cycle consists of several phases that a cell goes through to divide and produce new cells. These phases include G1, S, G2, and M phases.
2. Identify the purpose of each phase: The G1 phase is the first gap phase where the cell grows and carries out normal functions. The S phase is where DNA replication occurs, resulting in the duplication of chromosomes. The G2 phase is the second gap phase where the cell prepares for mitosis. The M phase is where mitosis and cytokinesis occur, leading to cell division.
3. Focus on the S phase: During the S phase, each chromosome is duplicated. This means that the DNA is replicated, resulting in two identical sister chromatids for each chromosome.
4. Recognize the importance of chromosome duplication: Chromosome duplication is crucial for ensuring that each daughter cell receives an identical set of chromosomes during cell division.
5. Conclude that the S phase is responsible for chromosome duplication: Based on the understanding of the cell cycle, it is clear that the S phase is the phase during which chromosomes are duplicated.