Crossover
Crossover is the process by which two
chromosomes paired up during prophase I of
meiosis exchange a distal portion of their
DNA. Crossover occurs when two
chromosomes, normally two
homologous instances of the same chromosome, break and connect to each other's ends. If they break at the same
locus, this merely results in an exchange of genes. This is the normal way in which crossover occurs. If they break at different loci, the result is a duplication of genes on one chromosome and a deletion on the other. If they break on opposite sides of the
centromere, this results in one chromosome being lost during
cell division.
Any pair of homologous chromosomes may be expected to cross over three or four times during meiosis. This aids evolution by increasing independent assortment, and reducing the genetic linkage between genes on the same chromosome.
For audio crossovers see electronic filters.