Linkage studies

Genetic linkage is the phenomenon whereby alleles at loci close together on the same chromosome will tend to be inherited together, because it will be rare for a crossover to occur between the loci at meiosis.

Large stretches of each parental chromosome are preserved intact when new chromosomes are formed during meiosis, but this phenomenon cannot be observed directly.

Instead, one may observe cosegregation of a marker with disease in multiply affected pedigrees.

Alternatively, one may test for increased marker allele-sharing between pairs of affected relatives, particularly affected sib pairs.

Linkage is a very long range phenomenon, so that only 300 markers may be sufficient to screen the whole genome.

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