From Qtl To Cg Candidate Gene To Qtg Quantitative Trait Gene

When gene maps of vertebrate species, including humans, are compared, the order of the genes in large chromosomal regions (depending on the particular pair of species compared) are often found to be the same. As a result, when a QTL has been mapped to a particular chromosomal region in a particular species, it is possible to look at the comparative gene map and identify the genes that are present in the comparable region in other species. Through bioinformatic data mining, all of the functional information accumulated across all living species on the genes in a given chromosomal region can be accessed. Among these genes may be those that have functions or expression patterns that make them attractive candidates to be the actual gene underlying the QTL. This can be tested by identifying markers within these candidate genes (CG), and then testing them for association with trait value by LD mapping. Candidate genes that show strong association with trait value become putative quantitative trait genes (QTG). Final confirmation that a putative QTG corresponds to the mapped QTL is difficult, but has been achieved successfully in a number of instances. In most cases, the identified QTG was one whose function was directly related to the physiology or development of the trait in question.

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