MICROSATELLITE HETEROZYGOSITY: FUNCTIONAL CONSTRAINTS ON THE DEVELOPMENT AND USE OF COMPREHENSIVE GENOMIC MAPS FOR LIVESTOCK

Authors: Beattie, Craig

Submitted to: Book Chapter
Publication Type: Book / Chapter
Publication Acceptance Date: 2/1/1996
Publication Date: N/A
Citation: N/A

Interpretive Summary: Microsatellites (ms) are abundant, multi-allelic, repetitive elements uniformly distributed throughout the genome of numerous species, including man. As ms are inherited codominantly, they have the potential to replace serum protein and red blood cell antigen polymorphisms for parental identification in livestock, assess genetic diversity or conservation within and between natural populations, and develop phylogenetic relationships. Most importantly, they can be extremely useful to first identify and then refine the genomic location of genes accounting for significant portions of the genetic variation of an economically important phenotype(s).

Technical Abstract: The lack of heterozygosity in outcrossed commercial species becomes extremely important when microsatellites (ms) are used to identify and refine the genomic location of genes accounting for significant portions of the genetic variation of an economically important phenotype(s). The problem is confounded when ms used to mark an interval are employed in marker-assisted selection (MAS), particularly within breeds in which one or more loci was not originally identified. A cluster of highly polymorphic markers linked to a locus of interest would facilitate identification of appropriate individuals to initiate introgression of favorable alleles into a breeding population. When taken to the logical conclusion of using ms in an extended selection program, it might be well to consider the impact of generation interval and selection intensity on the relative heterozygosity of those ms flanking a genomic locus in animals selected to introgress the associated positive phenotype. A short interval and intensive selection pressure may act to lower the heterozygosity or allelic frequency of the ms used in the selection process. Clusters of ms flanking a locus may be of some advantage. As desirable alleles in question become fixed and marker disequilibrium lost during selection as the process achieves its goals, we will need to move from selection on those marker alleles identifying the locus and develop more strategies (and markers) to account for the additional genetic variation within each trait.