chromatids break and may be reattached to a different homologous chromosome.
Chromosomal crossover (or crossing over) is the exchange of genetic material between homologous chromosomes that results in recombinant chromosomes during sexual reproduction. crossing over. crossing over, process in genetics by which the two chromosomes of a homologous pair exchange equal segments with each other. Crossing over occurs in the first division of meiosis. At that stage each chromosome has replicated into two strands called sister chromatids. The two homologous chromosomes of a pair synapse, or come together. Further genetic variation comes from crossing over, which may occur during prophase I of meiosis. In prophase I of meiosis, the replicated homologous pair of chromosomes comes together in the process called synapsis, and sections of the chromosomes are exchanged. Crossing over, or recombination, is the exchange of chromosome segments between nonsister chromatids in meiosis. Crossing over creates new combinations of genes in the gametes that are not found in either parent, contributing to genetic diversity. From Wikipedia, the free encyclopedia. Crossing over occurs between prophase 1 and metaphase 1 and is the process where homologous chromosomes pair up with each other and exchange different segments of their genetic material to form recombinant chromosomes. It can also happen during mitotic division, which may result in loss of heterozygosity. Best Answer: Crossing-over is another name for recombination or physical exchange of equal pieces of adjacent non-sister chromatids. When crossing-over occurs chromatids break and may be reattached to a different homologous chromosome.
https://en.wikipedia.org/wiki/Chromosomal_crossover http://www.infoplease.com/encyclopedia/science/crossing-over.html http://www.phschool.com/science/biology_place/labbench/lab3/crossovr.html http://www.encyclopedia.com/topic/crossing_over.aspx https://en.wikipedia.org/wiki/Chromosomal_crossover https://answers.yahoo.com/question/index?qid=20081215210534AALUBc8
crossing over occurs when?