What happens during the S phase?

What happens during the S phase?

• A. DNA transcription and RNA processing
• B. DNA replication
• C. Mitosis
• D. Cytokinesis

Answer: (B)

DNA replication happens during the synthesis phase of the cell cycle, when the cell duplicates its genome in preparation for division. This stage ensures that each daughter cell will receive a complete copy of the genetic material. During S phase, the two DNA strands unwind, replication forks form, and new strands are built by DNA polymerases in a semi-conservative manner—each new DNA molecule has one original strand and one newly synthesized strand. In complex cells, replication starts at multiple origins and proceeds in both directions, finishing before mitosis begins. After this phase, the cell checks the copied genome before entering mitosis to separate the chromatids, followed by cytokinesis to divide the cytoplasm. Transcription and RNA processing are ongoing activities during interphase, but they are not the defining event of this phase. Mitosis and cytokinesis are the stages of chromosome separation and cytoplasmic division that occur later in the cycle.

DNA replication happens during the synthesis phase of the cell cycle, when the cell duplicates its genome in preparation for division. This stage ensures that each daughter cell will receive a complete copy of the genetic material. During S phase, the two DNA strands unwind, replication forks form, and new strands are built by DNA polymerases in a semi-conservative manner—each new DNA molecule has one original strand and one newly synthesized strand. In complex cells, replication starts at multiple origins and proceeds in both directions, finishing before mitosis begins. After this phase, the cell checks the copied genome before entering mitosis to separate the chromatids, followed by cytokinesis to divide the cytoplasm.

Transcription and RNA processing are ongoing activities during interphase, but they are not the defining event of this phase. Mitosis and cytokinesis are the stages of chromosome separation and cytoplasmic division that occur later in the cycle.