Adithya V.

Cell Cycle

The cell cycle is the sequence of events that a cell goes through to grow and divide. It has two main phases:

1. Interphase (Preparation phase)
2. M Phase (Mitotic phase or Division phase)

1. Interphase

The cell prepares for division. It has three sub-phases:

🔹 G₁ Phase (Gap 1)

• The cell grows in size.
• New proteins and organelles are made.
• It is the period of active growth and normal cell function.
• The cell decides whether to divide or not.

🔹 S Phase (Synthesis)

• The cell copies (duplicates) its DNA.
• Each chromosome now has two identical sister chromatids.
• This is essential for proper division later.

🔹 G₂ Phase (Gap 2)

• The cell continues to grow.
• Prepares all necessary proteins and structures for division.
• Final check for DNA errors; repairs are made if needed.

2. M Phase (Mitotic Phase)

The actual division of the cell happens here. It has two parts:

🔹 Karyokinesis - Division of the nucleus

This includes 4 stages:

Prophase

• Chromosomes condense and become visible.
• Nuclear membrane starts to break down.
• Spindle fibers begin to form.

Metaphase

• Chromosomes line up at the center of the cell (metaphase plate).
• Spindle fibers attach to the centromere of each chromosome.

Anaphase

• Sister chromatids are pulled apart toward opposite poles of the cell.
• Each pole gets an identical set of chromosomes.

Telophase

• Chromosomes uncoil and become less visible.
• Nuclear membrane reforms around each set of chromosomes.
• The spindle fibers disappear.

🔹 Cytokinesis - Division of the cytoplasm

• The cell splits into two daughter cells, each identical to the original cell.

Summary Table