Describe crossing over. At which stage of meiosis does it occur? Name two functions of chiasmata.

Crossing over is the process in which homologous chromosomes exchange genetic material during meiosis, increasing genetic diversity by creating new combinations of alleles within the resulting gametes. This occurs during the prophase I stage of meiosis I, where homologous chromosomes form a synaptonemal complex and exchange genetic information, resulting in the formation of chiasmata. Chiasmata are points where homologous chromosomes physically exchange genetic material during the crossing over process. They serve two functions: maintaining the pairing of homologous chromosomes by holding them together and generating genetic diversity among the resulting gametes through the creation of new combinations of alleles.