Question

during the cell cycle, ________. *
cell cycle
gap 1
mitosis
gap 2
synthesis
dna is replicated once before mitosis and again before cytokinesis.
dna is replicated before mitosis begins.
dna is replicated directly after the completion of mitosis.
dna is replicated during mitosis.

Explanation:

The cell cycle consists of Gap 1 (G1), Synthesis (S), Gap 2 (G2), and Mitosis (M) phases. DNA replication occurs during the Synthesis (S) phase, which is before mitosis (M - phase) begins.

• Option 1: DNA is replicated only once in the S - phase of the cell cycle, not twice (before mitosis and before cytokinesis). Cytokinesis is the final step of M - phase, and no DNA replication occurs before it.
• Option 2: DNA replication occurs in the S - phase, and the S - phase is followed by G2 and then mitosis. So, DNA is replicated before mitosis begins.
• Option 3: After mitosis (in the G1 phase of the next cell cycle), the cell grows, and DNA replication (S - phase) occurs before the next mitosis, not right after the completion of mitosis.
• Option 4: Mitosis is for the division of the nucleus (distribution of replicated DNA to daughter nuclei). DNA replication does not occur during mitosis.

Answer:

DNA is replicated before mitosis begins.