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Mitotic crossover is a rare type of genetic recombination that may occur in some types of somatic cells during mitosis. Mitotic crossover may occur in organisms that do not have a cycle of sexual reproduction where chromosomal crossover would normally occur during meiosis to generate genetic variation. It can only occur in diploid cells and a pair of chromosomes is required for the crossover to occur.

The mitotic crossover results in the production of homozygous allele combinations in all heterozygous genes that are located on that chromosome arm distal to the crossover. Thus when a mitotic crossover occurs, genes that were previously recessive are expressed creating a new phenotype.

Mitotic crossover is known to occur in some asexually reproducing fungi, and in human cancer cells, where the crossover enables the expression of normally recessive cancer-causing genes.

[edit] References

• Griffiths et al. 1999. Modern Genetic Analysis. W. H. Freeman and Company.