genetic linkage

Also found in: Dictionary, Thesaurus, Financial, Encyclopedia, Wikipedia.
Related to genetic linkage: genetic map, Complete linkage


1. A chemical covalent bond.
2. The relationship between syntenic loci sufficiently close that the respective alleles are not inherited independently by the offspring; a characteristic of loci, not genes.
Farlex Partner Medical Dictionary © Farlex 2012
Genetic linkageclick for a larger image
Fig. 170 Genetic linkage . The phenotypes produced by a testcross.

genetic linkage

the association between genes located (linked) on the same chromosome, thus producing proportions of gametes that are not those expected by INDEPENDENT ASSORTMENT although, unless there is very close linkage, the same TYPES of gamete will be produced. Instead, there tends to be association of particular alleles together in the gametes (the ‘parental’ types, in the same combination as the parent), with other combinations being less frequent (see RECOMBINATION and CROSSING OVER). By convention the amount of recombination between linked genes is a direct measure of their distance apart along the chromosome, 1% recombination being equivalent to the MAP UNIT. The amount of recombination occuring is best measured in a TESTCROSS calculated from the total number of recombinant types in the testcross progeny as a proportion of the total progeny. For example, a testcross with genes in COUPLING produced the PHENOTYPES in Fig. 170 where the amount of recombination would be:

and the genes A and B could be represented on a GENETIC MAP as:

Had the two genes been independently assorting (i.e., on different chromosomes) roughly equal numbers of each phenotype would have been expected in the progeny (about 70). Similarly, since the maximum expected amount of recombination between two genes is 50%, if two genes are located more than 50 map units apart on the same chromosome they will appear to be independent of each other.

Collins Dictionary of Biology, 3rd ed. © W. G. Hale, V. A. Saunders, J. P. Margham 2005
References in periodicals archive ?
Pendulum, basic physical maps are instrumental to integrate the incipient available information, as the reference genetic linkage map already existing for this taxon.
If a relationship existed between certain genetic markers and a given phenotype--for example, if a variant of a marker occurred more commonly in family members with the phenotype than would be expected by chance--this served as evidence of genetic linkage.
Although the first duck genetic linkage map has been developed (Huang et al., 2006), it only spans 1,353.3 cM with an average interval distance of 15.04 cM.
Rps8 was placed on the genetic linkage map on the basis of the combination of homozygous resistant with the segregating class and the homozygous susceptible (3:1) with the molecular markers (Fig.
These analyses found that the "alcoholism or depression" phenotype showed significant evidence for genetic linkage to an area on chromosome 1.
Such an ability would aid genetic linkage studies and might provide more uniform populations in which to test experimental drugs.
ABSTRACT Genetic linkage maps were constructed for the noble scallop Chlamys nobilis Reeve on the basis of 373 amplified fragment length polymorphisms (AFLPs) and 9 microsatellite markers.
Washington, July 29 (ANI): A team of scientists has constructed a first-generation genetic linkage map for the saltwater crocodile Crocodylus porosus.
JoinMap Version 3.0: Software for the calculation of genetic linkage maps.
Such an approach would be complementary to ongoing genetic linkage studies for which candidate genes or haplotypes have been suggested or established but not confirmed.