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Reciprocal exchange of material between two paired chromosomes during meiosis, resulting in the transfer of a block of genes from each chromosome to its homologue. In contrast to genetic recombination (2), which is a phenotypic phenomenon, crossing-over is genotypic. Any even number of crossing-overs between two loci will cancel out phenotypically and no recombination will occur.
Farlex Partner Medical Dictionary © Farlex 2012
cross·ing-o·ver, cross-over (kraws'ing-ō'vĕr, kraws'ō-vĕr)
1. Reciprocal exchange of material between two paired chromosomes during meiosis, resulting in the transfer of a block of genes from each chromosome to its homologue.
2. The phenomenon that sound presented to one ear may be perceived in the other ear by passing around the head by air conduction or through the head by bone conduction.
Medical Dictionary for the Health Professions and Nursing © Farlex 2012
crossing-overThe exchange of short lengths of CHROMATIDS between homologous pairs of chromosomes during one of the stages of division (meiosis) that occurs when the eggs (ova) and sperms are being formed. Crossing-over is one of the ways in which a random redistribution of genes occurs and ensures that the combinations of genes in each sperm or egg differs from the combinations in the cells of the parents.
Collins Dictionary of Medicine © Robert M. Youngson 2004, 2005