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

• A. Prophase
• B. Interphase
• C. Metaphase
• D. Telophase

Answer: (B)

Replication of chromosomes occurs during interphase, specifically in the S phase (synthesis phase) of interphase. During this phase, the cell undergoes preparation for division by duplicating its DNA, ensuring that each daughter cell will receive an identical copy of the genetic material. This is a critical step in the cell cycle, as it allows for proper genetic continuity and is essential for cell growth and reproduction.

In contrast, prophase, metaphase, and telophase are all stages of mitosis, which is the process of dividing the replicated chromosomes and distributing them into two new nuclei. During prophase, the chromatin condenses into visible chromosomes, but replication has already occurred prior to this phase. Metaphase involves the alignment of chromosomes at the cell's equatorial plane, while telophase is characterized by the reformation of nuclear membranes around the separated sets of chromosomes. Therefore, none of these stages involve the replication of chromosomes, which is why interphase is the correct answer.