Meiosis is a type of cell division that occurs only in the sex organs (gonads). The male sex organ is called the testes and the female sex organ is called the ovaries. The purpose is to create sex cells or gametes (ova and sperm) which contains half the number of chromosomes that are in the parent cell. Each iteration of meiosis produces four daughter cells that are genetically unique. There are two main processes that occur during meiosis that ensure each of the daughter cells are genetically unique:
Independent assortment: Homologous chromosomes line up randomly during meiosis. This means that it is completely random which combination of alleles ends up in any particular gamete.
Crossing over: This is when homologous chromosomes exchange sections of the chromosomes (alleles). This therefore leads to a completely new combination of alleles on the chromosome. Because of crossing over, each gamete will contain a different combination of alleles.
This is important because when the gametes fuse during fertilisation, they create genetically unique zygotes, leading to differences between individuals in a population