Meiosis

Meiosis is a process where a cell divides into 4 individual cells. It is a process where one diploid cell divides to generate 4 haploid cells known as gametes. During this process, DNA that is packed in structures known as chromosomes undergo replication followed by 2 times of cell division. This results in formation of 4 cells called gametes which can be a mature sperm or egg.

There are 8 phases to describe the meiosis process. They are meiosis 1 prophase 1, metaphase 1, anaphase 1 and telophase 1. Meiosis 2 includes prophase 2, metaphase 2, anaphase 2.

Prophase  1 is where the nuclear envelope disintegrates and DNA is exchanged between homologous chromosomes. This process is called chromosomal crossover. This process allows for each 2 homologue chromosomes to break and reconnect but with the difference pieces. This combination is the source of genetic variations. There are various sub-variations during prophase 1 namely, leptotene, zygotene, pachytene, diplotene, diakinesis and the synchronous processes.

Metaphase 1: The homologous chromosomes (4 chromatids) line up on the equator. The spindle microtubules move towards the equator of the cell.

Anaphase 1: The Kinetochore also known as the bipolar spindles or microtubules shorten causing the homologous pairs to be separated. One chromosome of each pair moves to opposite poles.

Telophase 1: It is here that the chromosomes arrive at the poles and they uncoil. This process effectively reduces chromosomes from diplod to haploid and division takes place. 

Another round of cell division takes place leading to the formation of haploid cells. This process has been called meiosis2 leading to formation of 4 cells and halving of chromosomes. The 4 stages of Meiosis 2  are: Prophase 2, Metaphase 2, Anaphase 2, and Telophase 2. This step is similar to mitosis.

Prophase 2: The chromosomes shortens, condenses, thickens and becomes visible. The centrioles move to the poles and rearrange onto spindle fibers and prepares for the second meiotic division.

Metaphse 2: The centromeres attach to the spindles from the centrioles and chromosomes line up along the equator.

Anaphase 2: The centromeres are cleaved allowing the chromatids to move to the opposite poles.

Telophase 2: The chromatids reach opposite sides of the poles. The chromosomes lengthen and the spindles disappear. Nuclear envelope forms around the chromosomes and cytokinesis occurs.