DNA replication occurs in which phase of cell growth

DNA replication takes place during the S phase, which stands for Synthesis phase of the cell cycle. This phase is part of the Interphase, which is the period between two cell divisions when the cell prepares itself for the next mitotic or meiotic division.

The Interphase has three main stages:
  1. G1 phase (Gap 1) – The cell grows and carries out normal functions.
  2. S phase (Synthesis) – This is the stage where DNA replication occurs.
  3. G2 phase (Gap 2) – The cell prepares for division by synthesising proteins and other components.

What Happens in the S Phase:

In this phase, the entire genetic material (DNA) of the cell is copied. Each chromosome makes an exact duplicate of itself, forming two sister chromatids joined at the centromere. These chromatids will later be separated into daughter cells during mitosis or meiosis.

This replication is semi-conservative, meaning each new DNA molecule contains one old strand and one newly synthesized strand. The process is highly regulated and involves enzymes like DNA helicase, DNA polymerase and ligase.

By the end of S phase, the amount of DNA in the nucleus doubles, but the chromosome number remains the same. For example, in humans, cells remain diploid with 46 chromosomes, but now each chromosome has two chromatids.






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