crossing over

The exchange of corresponding segments between chromatids of paired (homologous) chromosomes; it is a process inferred cytologically from new associations of parts of chromosomes, both of which may be observed in an exchange of factors and in combinations of factors differing from those that came in with the parents; the term `genetic cross-over' may be applied to these new gene combinations; its genetic consequence is the recombination of linked genes. Cf. Recombination.