Meiosis

Meiosis is cell division, which is how genes are inherited from parent to offspring, through sexual reproduction. Every Person has 46 chromosomes in their body. Half of your chromosomes come from your mother and half from you father. These are found in the gamates, which means they are in either the egg of a female or the sperm of a male. When the egg is fertilized, it becomes diploid, meaning is has two sets of chromosomes. Meiosis goes through two processes, each containing different phases. In meiosis I the parent cell divides to two identical daughter cells. In meiosis I there are 4 phases: prophase, metaphase, anaphase and telophase.
Prophase I: the Chrosomes are duplicated during interphase I, before Prophase I. During prophase the duplicated homologous ( same) pairs of chromosomes go through crossing - over. This is just when the chromosome pairs, also known as sister chromatids, cross - over each other and exchange parts of the chromosome parts. This allows for varieties in genes. Prophase takes the longest time out of all of the other phases. Also during prophase the nucleolus disappears and the meiotic spindles start to form on opposite poles of the cell.
Metaphase I: During Metaphase I the homologous pairs of chromosome line up on the metaphase plate, in random orders. The the spindle fibers come down from the poles and attach to the homologous chromosomes.
Anaphase I: In anaphase I the spindle fibers pull the chromosomes to opposite sides of the cell. the tetrads stay connected at the centromere. They are not yet seperated, this takes place during anaphase II.
Telophase I: During Telophase I the chromosome pairs are on two different sides of the cell, which makes two daughter cells that are each haploid ( 23 chromosomes ) and each contain two sets of chromatids. the spindle disappears and cytokinesis starts. In cytokinesis a cleavage furrow forms, which makes the cells into two seperate cells. . This concludes meiosis I and meiosis II proceeds, starting with Prophase II.


Meiosis II: Meiosis II takes the two daughter cells and divides them into four daughter cells. This process starts with Prophase II.

Prophase II: The centrioles duplicate. No new chromosomes are replicated during meiosis II. the nuclear envelope disappairs and the spindles form.

Metaphase II: single chomosomes form along the metaphase plate. the kinetochore of the sister chromatids are connected to the kinetochore microtubles coming from the poles.

Anaphase II: the centromeres split and the to sister chromatids move to opposite sides of the poles, these are now seperate chromosomes.

Telophase II: cytokinesis forms four daughter haploid cells which because of crossing over results in recombination of the parents chromosomes. This then concludes the meiosis process.