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Modern Genetic Analysis
5. Recombination of Genes
Key Concepts

Two genes close together on a homologous chromosome pair do not assort independently at meiosis.
Recombination produces genotypes with new combinations of parental alleles.
A pair of homologous chromosomes can exchange parts by crossing-over.
Recombination results from either independent assortment (50 percent recombinant frequency) or crossing-over (recombinant frequency between 0 and 50 percent).
Gene loci on a chromosome can be mapped relative to one another by measuring the frequencies of recombinants produced by crossing-over.
Map distances based on recombination measurements are roughly additive.
Rarely, crossing-over occurs at mitosis.
Crossing-over occurs by the formation of a DNA segment that is a heteroduplexa strand from one parental chromatid and a strand from the other.

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