Vemula Sharathbabu

The cell cycle is an ordered series of events that leads to cell division and the production of two new daughter cells. It is divided into two main stages: Interphase and the M phase.

Interphase: The Preparation Stage 

This is the longest phase of the cell cycle, where the cell grows, synthesizes DNA, and prepares for division. It's divided into three sub-phases.

G_1 Phase (Gap 1): This is the first growth phase. The cell increases in size and synthesizes proteins and RNA necessary for DNA synthesis. It carries out its normal metabolic functions. The cell also assesses its environment to decide whether to proceed with division.

S Phase (Synthesis): The most crucial event of this phase is DNA replication. The cell makes an exact copy of its DNA. At the end of the S phase, each chromosome consists of two identical sister chromatids joined at a centromere. The amount of DNA in the cell doubles.

G_2 Phase (Gap 2): This is the second growth phase. The cell continues to grow and produce proteins and organelles, such as microtubules, required for the upcoming division. The cell double-checks the duplicated chromosomes for errors and makes any needed repairs before entering mitosis.

M Phase (Mitosis): The Division Stage 

This is the phase where the cell divides its copied DNA and cytoplasm to make two new cells. Mitosis, the division of the nucleus, is divided into four stages.

Prophase:

The chromosomes condense and become tightly coiled, making them visible under a microscope.

The nuclear envelope and nucleolus begin to break down and disappear.

In the cytoplasm, the spindle fibers (made of microtubules) begin to form from structures called centrosomes, which move to opposite poles of the cell.

Metaphase:

The fully condensed chromosomes align along the metaphase plate, an imaginary line in the center of the cell.

The spindle fibers attach to the centromere of each chromosome, ensuring that each sister chromatid is attached to a spindle fiber from opposite poles.

Anaphase:

The proteins holding the sister chromatids together are cleaved.

The sister chromatids separate and are pulled apart by the shortening spindle fibers toward opposite poles of the cell.

Once separated, each chromatid is now considered a full-fledged chromosome.

Telophase:

The chromosomes arrive at opposite poles of the cell and begin to decondense, returning to their string-like form.

A new nuclear envelope re-forms around each set of chromosomes, creating two distinct nuclei.

The spindle fibers break down.

This stage is usually followed by cytokinesis, where the cytoplasm divides to form two separate, genetically identical daughter cells.