Meiosis contributes to genetic recombination via independent assortment of homologous chromosomes and crossing-over events. Genetic recombination is vital for the existence of genetic variability within a species.
Meiosis is cell division specific to sex cells and involves more than the simple copying of genetic material that occurs during mitosis. Most of the cells in the human body contain 46 chromosomes, half from the mother and half from the father. These are diploid cells. The goal of meiosis is to create reproductive haploid cells, which are cells with only 23 chromosomes. This is necessary so that, after fertilization, an offspring's cells contain the appropriate chromosome number. Meiosis also provides for the random alignment and recombination of genetic material that ensures a person is never a copy of one parent or the other.
Chromosomes exist in pairs as homologous chromosomes. One chromosome from each pair comes from the maternal parent, the other from the paternal parent. During meiosis homologous chromosomes separate independently. Independent assortment means that there is no mechanism by which these chromosomes associate with one another. Because of this, the sex cells that are the end product of meiosis may contain any combination of maternal and paternal chromosomes.
Sometimes, when homologous chromosomes are paired, each may lose a small portion that then reconnects to the other member of the pair. This is crossing over. When crossing over occurs, homologous chromosomes trade genetic material with one another.