Meiosis

• Meiosis is the process of cell division that occurs in sex organs (ovaries and testes) that produce the sex cells or gametes (ova and sperm)
• In many species, each somatic cell have pairs of chromosomes (homologous chromosomes). This is known as the diploid number, 2n. The alleles of the genes in each pair can be different (eg B for brown eye and b for blue eye) because one chromosome comes from the father and one from the mother.
• The gametes produced in meiosis have half the diploid number of chromosomes (one from each pair)-known as the haploid number,n.
• When the ovum and sperm fuse in fertilisation, the diploid number of chromosomes is restored in the zygote (fertilised ovum). Subsequent mitotic divisions of the zygote to form embryo maintain the diploid number.