During the mitotic cell cycle, how many times is the genome (DNA) replicated before a cell completes mitosis?

• A. DNA is continuously replicated throughout mitosis
• B. Once, during prophase of mitosis
• C. Once, during S phase of interphase
• D. Twice, once in G1 and once in S phase

Answer: (C)

Verified step by step guidance

1. Understand the phases of the cell cycle: G1 (gap 1), S (synthesis), G2 (gap 2), and M (mitosis).
2. Recall that DNA replication occurs during the S phase of interphase, which is before mitosis begins.
3. Recognize that during mitosis itself, the DNA is not replicated; instead, the replicated chromosomes are separated into daughter cells.
4. Note that DNA replication happens only once per cell cycle to ensure each daughter cell receives an identical copy of the genome.
5. Conclude that the genome is replicated once during the S phase of interphase, prior to mitosis.