Inheritance of 12 microsatellite loci in Oncorhynchus mykiss

Four full-sib families of Oncorhynchus mykiss were used to study the inheri tance of allelic variation at 12 microsatellite loci. The loci examined wer e previously characterized in six different species from the family Salmoni dae, Of the 48 genotypic ratios observed (12 loci x 4 crosses), disomic seg regation of codominant autosomal alleles was established in 24 of 31 inform ative tests, The seven tests that did not conform to Mendelian ratios can b e explained by the presence of null alleles (One mu 14 and Omy77) and a loc us (One mu 1) that may be tandemly duplicated. Three significant pairwise l inkage associations were observed between One mu 1 and Omy207, Ssa85 and On e mu 11, and the two loci amplified by One mu 1 primers, indicating these l oci are not asserting independently. The presence of unexpected heteroduple x structures in One mu 11 electropherograms in one cross prompted the seque ncing of similar microsatellite electromorphs. Sequence differences reveale d size homoplasy, that is, the electromorphs were identical in state but th ey were not identical by descent. These results demonstrate the need to con duct comprehensive species-specific inheritance studies for microsatellite loci used in population genetic or kinship analyses. Discovery of these fou r attributes by examining a small number of loci in four families suggests that they are common across microsatellite loci overall.