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Analysing Cells
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Cell Cycle

The cell cycle is the process that cells go through to grow, copy their DNA, and split into two new cells. This cycle is how our bodies grow, heal, and stay healthy.

It happens in several steps:

The first three steps (G₁, S, and G₂) are called interphase. This is when the cell does most of its work, like growing and preparing for division.

In this article, we’ll walk through each part of the cell cycle in simple terms, so you can understand how cells work and why this process is so important.

Mitosis

This stage can be further subdivided into 4 stages: prophase, metaphase, anaphase, and telophase. Have a look at the diagrams so you are able to identify each stage in an exam situation.

The first subphase is prophase, during this the nuclear membrane (membrane surrounding the nucleus) begins to disappear, spindles begin to develop, and most importantly, the DNA condenses from a spaghetti-like mess to the distinct chromosomes you can see.

diagram of prophase in cell cycle

The next stage is metaphase where the nuclear membrane has disappeared and the chromosomes line up on the cell equator. It is closely followed by anaphase where the spindle fibres pull apart the chromatids to opposite poles of the cell.

the metaphase and anaphase of the cell cycle

The final stage is telophase, this is where a nuclear membrane forms around the sets of chromosome and the cell begins to seperate into two.

The Phases of Mitosis: How Cells Divide Step by Step

Mitosis is the process where a single cell divides to create two identical cells, each with the same genetic information. This is how our bodies grow, heal wounds, and replace old cells. Let’s walk through each phase of mitosis in a simple and easy-to-understand way:

Prometaphase – Getting Ready to Line Up

The nuclear envelope (the outer layer around the nucleus) breaks apart. This lets spindle fibers (tiny threads) reach the chromosomes. Each chromosome is now ready to be moved, and the spindle fibers attach to a special area on the chromosome called the centromere.

Metaphase – All Lined Up

Now, the chromosomes are moved to the middle of the cell. They line up in a straight row, which makes it easier to divide them equally. This stage is like the cell making sure everything is perfectly in place before moving forward.

Anaphase – Splitting Apart

The spindle fibers pull the chromosomes apart. Each chromosome splits into two identical halves, called sister chromatids, and these are pulled to opposite sides of the cell. This ensures that each new cell will get an exact copy of the DNA.

Telophase – Building New Nuclei

Once the chromatids reach the opposite ends, new nuclear membranes form around them. The chromosomes start to relax and turn back into their original string-like shape. At this point, you can already see two separate nuclei forming inside one cell.

Cytokinesis – The Final Split

This is the final stage. The cell’s cytoplasm divides, and the cell physically splits into two.

End result: Two completely new cells, each with the same DNA as the original cell.

What Is Meiosis

Meiosis is a special type of cell division that produces gametes — sperm and egg cells — in sexually reproducing organisms. Unlike regular cell division (mitosis), which creates identical cells, meiosis ensures that each gamete contains half the usual number of chromosomes. This is essential for keeping the correct number of chromosomes when sperm and egg come together during fertilization.

Key Purpose of Meiosis

Meiosis Happens in Two Stages

Meiosis takes place in two main stages: Meiosis I and Meiosis II, each with multiple phases. But DNA is copied only once, before everything begins.

Meiosis I: Reducing the Chromosome Number

Meiosis First Stage

Prophase I – Crossing Over Begins

This phase has 5 sub-stages:

Prometaphase I

Metaphase I – Chromosomes Line Up

Anaphase I – Homologous Chromosomes Separate

Telophase I & Cytokinesis – Two Cells Form

Meiosis II: Separating the Chromatids

Meiosis Second Stage

Meiosis II is similar to mitosis. Each haploid cell now divides again, this time splitting the sister chromatids apart.

Prophase II

Metaphase II

Anaphase II

Telophase II & Cytokinesis

In males, these become four sperm cells. In females, typically one egg and a few smaller, non-functional cells are formed.

How Meiosis Creates Genetic Diversity

Meiosis plays a key role in producing variation in offspring through:

  1. Crossing Over – DNA is exchanged between chromosome pairs in Prophase I.
  2. Independent Assortment – Chromosomes line up randomly in Metaphase I and II.
  3. Mixing of Parental Genes – Every gamete is different, increasing diversity in the next generation.

Summary: Why Meiosis Matters

Feature Meiosis I Meiosis II
Main Purpose Reduce chromosome number Separate sister chromatids
DNA Replication Happens once before Meiosis I Does not happen again
Final Outcome 4 haploid cells (gametes), all genetically unique

Meiosis is essential for sexual reproduction, and it ensures that each generation starts with a fresh mix of genetic material, which drives evolution and biological diversity.

Updated: 23 April 2025