Inheritance of 12 microsatellite loci in Oncorhynchus mykiss

Abstract

Four full-sib families of Oncorhynchus mykiss were used to study the inheritance of allelic variation at 12 microsatellite loci. The loci examined were previously characterized in six different species from the family Salmonidae. Of the 48 genotypic ratios observed (12 loci x 4 crosses), disomic segregation of codominant autosomal alleles were established in 24 of 31 informative tests. The seven tests that did not conform to Mendelian ratios can be explained by the presence of null alleles (Oneμ14 and Omy77) and a locus (Oneμ1) that may be tandemly duplicated. Three significant pairwise linkage associations were observed between Oneμ1 and Omy207, Ssa85 and Oneμ11, and the two loci amplified by Oneμ1 primers, indicating these loci are not assorting independently. The presence of unexpected heteroduplex structures in Oneμ11 electropherograms in one cross prompted the sequencing of similar microsatellite electromorphs. Sequence differences revealed size homoplasy, that is, the electromorphs were identical in state but they were not identical by descent. These results demonstrate the need to conduct comprehensive species-specific inheritance studies for microsatellite loci used in population genetic or kinship analyses. Discovery of these four attributes by examining a small number of loci in four families suggests that they are common across microsatellite loci overall.