At what stage of the cell cycle are chromosomes duplicated?

• A. During the G2 phase
• B. During mitosis
• C. During the G1 phase
• D. During the S phase

Answer: (D)

Verified step by step guidance

1. Understand the cell cycle: The cell cycle consists of several phases, including G1, S, G2, and M (mitosis). Each phase has specific functions and activities related to cell growth and division.
2. Identify the purpose of each phase: The G1 phase is primarily for cell growth and preparation for DNA replication. The S phase is where DNA replication occurs, leading to chromosome duplication. The G2 phase involves further growth and preparation for mitosis. Mitosis is the phase where the cell divides.
3. Focus on the S phase: During the S phase, the cell synthesizes a complete copy of the DNA in its nucleus. This is the stage where chromosomes are duplicated, ensuring that each daughter cell receives an identical set of chromosomes.
4. Consider the role of DNA replication: DNA replication is a crucial process during the S phase, involving the unwinding of the DNA double helix and the synthesis of new strands by DNA polymerase enzymes.
5. Review the sequence of the cell cycle: The cell cycle progresses from G1 to S to G2 and finally to mitosis. Chromosome duplication is specifically associated with the S phase, which is essential for accurate cell division.