Question

during the cell cycle,
a. dna is replicated before mitosis begins.
b. dna is replicated once before mitosis and again before cytokinesis.
c. dna is replicated directly after the completion of mitosis.
d. dna is replicated during mitosis.

Explanation:

To solve this, we recall the cell cycle phases. The cell cycle has interphase (G1, S, G2) and mitotic phase (mitosis, cytokinesis). DNA replication occurs in the S - phase of interphase, which is before mitosis starts.

• Option A: DNA is replicated in S - phase (part of interphase) before mitosis, so this is correct.
• Option B: DNA is replicated only once in S - phase, not again before cytokinesis, so this is wrong.
• Option C: After mitosis, the cell enters G1 phase, and DNA replication occurs in S - phase (not directly after mitosis), so this is wrong.
• Option D: Mitosis is the division of the nucleus; DNA replication happens in interphase, not during mitosis, so this is wrong.

Answer:

A. DNA is replicated before mitosis begins.