Mitotic crossover

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.

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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 normal human cells, where the event may allow normally recessive cancer-causing genes to be expressed and thus predispose the individual to the development of cancer.

References

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