10.1 Meiosis

Meisosis I


At the prophase I stage of meiosis I the chromosomes have shortened and thickened by supercoiling. .The homologous chromosomes pair up to form what are called bivalents. This is where crossing over and chiasmata formation can happen.

The centrioles have moved to the poles of the cell and microtubules start growing towards the chromosomes.

At the metaphase I stage of meiosis I the bivalents line up at the equator of the cell. The microtubules join to the centromere of the chromosomes. The chiasmata slide down the chromosomes changing their shape. Now the bivalents are starting to move apart.

In anaphase I of meiosis I the bivalents are separated to opposite poles so the chromosome number is halved.

The final stage of meiosis I is telophase I followed by cytokinesis. This is where two new haploid cells are formed. These cells will then enter meiosis II without any further replication of DNA as each chromosome consists of two chromatids. This means 2 haploid cells have been formed from1 diploid cell in meiosis Iimage


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