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Post a Lesson This is the longest phase where the cell prepares for division. It is divided into three parts:
a) G₁ Phase (Gap 1):
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The cell grows in size.
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Organelles increase in number.
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The cell performs its normal functions.
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It checks for DNA damage and decides whether to proceed to the next phase.
b) S Phase (Synthesis):
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DNA replication occurs.
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Each chromosome makes an identical copy (sister chromatids).
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The cell now has double the amount of DNA.
c) G₂ Phase (Gap 2):
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The cell continues to grow.
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Prepares all the necessary proteins and organelles for mitosis.
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Checks for any DNA damage after replication.
2. M Phase (Mitotic Phase)
This is when the cell divides. It has two parts:
A) Mitosis (division of the nucleus):
Mitosis is further divided into four stages:
i) Prophase:
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Chromosomes condense and become visible.
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Nuclear envelope starts to break down.
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Spindle fibers begin to form from centrioles.
ii) Metaphase:
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Chromosomes line up at the center (metaphase plate) of the cell.
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Spindle fibers attach to the centromere of each chromosome.
iii) Anaphase:
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Sister chromatids are pulled apart to opposite poles of the cell.
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Each chromatid is now considered an individual chromosome.
iv) Telophase:
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Chromosomes start to de-condense.
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Nuclear envelopes re-form around the two sets of chromosomes.
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Spindle fibers disappear.
B) Cytokinesis (division of the cytoplasm):
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The cell splits into two daughter cells.
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Each has the same number of chromosomes as the parent cell.
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