Significance of Meiosis

Meiosis is not merely a variant form of cell division; it is a biological necessity for every organism that reproduces sexually, and its significance rests on two distinct, equally essential consequences of the process: the halving of the chromosome number, and the generation of genetic variation.

The first significance concerns chromosome number. Sexual reproduction works by the fusion of two gametes -- one from each parent -- at fertilisation, to form a single zygote. If the gametes themselves carried the full diploid (2n) chromosome number of the parent's body cells, then every act of fertilisation would double the chromosome number in the resulting zygote, and this doubling would repeat and compound with every successive generation, quickly producing an unworkable and ever-increasing chromosome count. Meiosis prevents this by halving the chromosome number during gamete formation, from diploid (2n) to haploid (n), so that when two haploid gametes fuse at fertilisation, the diploid number is exactly restored in the zygote, rather than doubled. In this way, meiosis is what allows the chromosome number characteristic of a species to remain constant, generation after generation, despite sexual reproduction. …