How is DNA replicated during the cell cycle?

• A. DNA replication is semi-conservative, where each new DNA molecule consists of one old strand and one new strand.
• B. DNA replication is dispersive, where the original DNA molecule is randomly fragmented and reassembled with new DNA.
• C. DNA replication occurs only in the G1 phase of the cell cycle.
• D. DNA replication is conservative, where the original DNA molecule is preserved and a completely new molecule is synthesized.

Answer: (A)

Verified step by step guidance

1. Understand that DNA replication is a critical process that occurs during the cell cycle to ensure that each daughter cell receives an exact copy of the DNA.
2. Recognize that DNA replication is described as 'semi-conservative'. This means that each of the two new DNA molecules consists of one original (parental) strand and one newly synthesized strand.
3. Identify the phase of the cell cycle where DNA replication occurs. DNA replication takes place during the S phase (Synthesis phase) of the cell cycle, not the G1 phase.
4. Differentiate between the terms 'semi-conservative', 'conservative', and 'dispersive' replication. In semi-conservative replication, each new DNA molecule retains one of the original strands. In conservative replication, the original DNA molecule is preserved intact, and a completely new molecule is synthesized. In dispersive replication, the original DNA is fragmented and reassembled with new DNA, which is not how DNA replication occurs in cells.
5. Conclude that the correct description of DNA replication is semi-conservative, occurring during the S phase of the cell cycle, ensuring genetic continuity across cell generations.