genetic linkage


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Related to genetic linkage: genetic map, Complete linkage

link·age

(lingk'ăj),
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.
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.

References in periodicals archive ?
Researchers determine the influence of genetic factors on development of alcohol dependence and/or habitual smoking using family studies, genetic linkage analyses, and candidate gene association studies.
Emily might decide she doesn't want to participate in genetic linkage studies now but might bank some of her DNA to be available for future studies when technology has evolved further.
Before the bovine genome sequencing project, a genetic linkage map of the bovine genome had been constructed that provided a basis for further mapping (Barendse et al.
AFLPs have been used to fingerprint accessions, to determine genetic linkage mapping, and to analyze genetic diversity (Young et al.
In contrast to genetic linkage studies that used 300-400 genetic markers, this GWAS used nearly 98,000 genetic markers called single-nu-cleotide polymorphisms (SNPs), yielding more than 20 million bits of data.
The remaining ten chapters address molecular markers and their detection and applications; types of mapping populations, methods of their generation, and applications; basic concepts and schematic depiction of construction of genetic linkage maps; concepts and strategies of mapping genes controlling qualitative and quantitative traits on framework linkage maps; rationale, methodologies, and implications of comparative mapping; principles, strategies, and outcomes of map-based cloning; recent advances in plant genomics and genome initiatives; and computer and software issues of plant molecular mapping and breeding.
Genetic linkage studies of thyroid peroxidase (TPO) gene in families with TPO deficiency.
Applications include genetic linkage studies of inherited disease in families, cancer genetics, and population genetics.
Mice with the desired trait are then bred to a known mouse strain for genetic linkage analyses to identify the genetic mutation causing the trait of interest.
Although genetic linkage analysis identified no significant genetic link to endometriosis for the entire cohort, it did uncover the first suggestion of a significant linkage between one particular chromosome and endometriosis in the 399 families with stage II-IV disease.
Using populations developed by collaborating scientists and segregating for resistance to witches' broom and frosty pod, we're producing genetic linkage maps using microsatellite markers.