biologia7

Meiosis is the process of cell division that results in gametes, such as sperm or egg cells, with half the normal number of chromosomes. There are two rounds of division, meiosis I and meiosis II. In meiosis I, homologous chromosomes pair up and separate, resulting in two cells each with half the original number of chromosome pairs. Crossing over can also occur, where homologous chromosomes exchange genetic material. In meiosis II, sister chromatids separate to produce four gametes each with a single set of chromosomes derived from the original cell. Meiosis introduces genetic variability through independent assortment of homologous chromosomes and crossing over.