How is meiosis different to mitosis?

Meiosis only takes place in the reproductive organs of plants and animals as opposed to throughout the body like mitosis. Meiosis results in the production of 4 genetically different, haploid gametes as opposed to mitosis’s  2 genetically identical diploid daughter cells. Meiosis follows the same basic pattern as mitosis but it has two divisions instead of one.  It is easy to remember the stages of mitosis and meiosis with the acronym PMAT:

Prophase

Metaphase

Anaphase

Telophase

The first division during meiosis is referred to as meiosis I and has some crucial differences to a mitotic division.

Prophase I

As in mitosis centrioles migrate to opposite poles and the spindle is formed and chromosomes become shorter and thicker.

Unlike in mitosis at this point homologous chromosomes associate in pairs called bivalents. This results in crossing over: Chromatids wrap round their homologous counterpart and then partially repel forming chiasmata where exchange of DNA can occur, creating variance with in chromosomes.

Metaphase I

The bivalents now align themselves at the equator of the spindle, the maternal and paternal chromosomes are randomly aligned resulting in a random combination of maternal and paternal chromosomes, this is called independent assortment.

Anaphase I

The bivalents are now separated with their chromosomes pulled to opposite sides by the spindle.

Telophase I

Unlike in mitosis the chromosomes now stay in their condensed form ready for mitosis II. Animal cells undergo cytokinesis here but many plant cells move straight on to meiosis II.

Meiosis II is almost identical to mitosis; the only difference is the cells are haploid.

Prophase II

A new spindle develops at right angles to the old one.

Metaphase II

Individual chromosomes line up at the equator.

Anaphase II

The chromosomes are divided at the centromere into chromatids which are pulled to opposite poles.

Telophase II

The nuclear envelop reforms and cytokinesis takes place.