What is a haploid cell and why is it important?
A cell containing one set of chromosomes. In meiosis, the nucleus of a cell divides twice. A single cell produces four cells by the end of meiosis. In sexually reproducing diploid animals (having two sets of chromosomes per cell), meiosis occurs during formation of the gametes (sex cells – see ovum), so that the gametes are haploid (having only one set of chromosomes – half the number of chromosomes of the parent cell). When the gametes unite during fertilization, the diploid condition is restored. Meiosis gives rise to variation. This is an important part of sexual reproduction. The variation produced is inherited, which means that evolution can take place as a result of the natural selection of certain variants to suit a changing environment. The way that meiosis gives rise to variation is by recombining genes from chromosomes in new ways. When the number of chromosomes is halved, there is some randomness in the way parts of chromosomes are selected to go into the gametes.
