What is Meiosis?

Diploid cells within human testes or ovaries produce haploid sperm or eggs by undergoing two divisions during meiosis.

The first division meiosis I, begins with diploid cells in which chromosomes have replicated, appearing x like in shape. The paternally and maternally inherited chromosomes exchange information between them during crossing over, creating genetic diversity.

Other changes during this period result in a microtubule-based framework that separates the chromosomes so that they are randomly but evenly partitioned between opposite ends of the cell. The cell then splits forming a novel pair of haploid cells.

Every x in these newly formed structures is individually termed a chromosome, is composed of two copies of the same chromosome, termed sister chromatids.

During the second division, meiosis II, a similar arrangement of microtubules breaks apart sister chromatids. This again yields haploid cells, with the key difference being that the chromosomes are no longer replicated and appear as I's when condensed.

Depending on whether meiosis occurs in the testes or ovaries, it produces either four sperm or one mature egg and smaller cells that later dissolve.

The fertilization of an egg produces a unique diploid individual, which is genetically distinct from its parents due to the events of meiosis.