Centimorgan [cM]

Unit of genetic recombination frequency for gene loci or markers on the same chromosome. A centimorgan is not an absolute measure, but a relative one. 1 centimorgan corresponds to a recombination frequency of 1%. The term centimorgan is used in two ways:

    • relative distance The relative distance between two gene loci on the same chromosome. Example: if the progeny shows recombination between two loci is 1%, then distance between both loci positions is said to be 1 cM.
    • probability for genetic linkage / crossing-over

The probability that two genes on the same chromosome will recombine independent of each other (uncoupled) during meiosis. Example: 1 cM corresponds to a chance of 1% that a marker will become separated from a second marker on the same chromosome due to crossing-over at meiosis.