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Year 10 iGSCE - Biology

Unlike mitosis, meiosis is a special form of division which only occurs in the sex cells. There are a few key differences between mitosis and meiosis.

MEIOSIS

Meiosis starts with a special body cell which live in the sex organs. These cells are like any other cell, in that they contain a full set of chromosomes.

When they divide however, they create 4 daughter cells instead of 2.

Each daughter cell contains only ½ the amount of chromosomes as the parent cell.

The cells produced are called gametes.

In humans each gamete has only 23 chromosomes.

Due to crossing over and random assortment of chromosomes, no two gametes are alike.

This creates a wide range of genetic variation.

Click here for a quick worksheet on meiosis

Basic steps of Meiosis  

1. Similar chromosomes pair up


2. Chromosomes swap sections of DNA (crossing over)


3. Chromosomes line up in their pairs


4. Pairs are pulled apart  and 2 cells are formed


5. Chromosomes line up as in mitosis and divide again


6. 4 cells are formed, each with ½ the chromosomes of the parent cell.