Parentage testing and linkage analysis in the horse using a set of highly polymorphic microsatellites

Ten (TG)n positive clones, isolated from an equine genomic library and sequenced, contained 12-19 uninterrupted TG repeats. Primers for polymerase chain reaction (PCR) were synthesized and nine of these (TG)n loci (HTG7-15) were successfully amplified and utilized in this study together with five previously reported equine microsatellite loci (HTG2-6). The PCR products were analysed by polyacrylamide gel electrophoresis followed by automated laser fluorescence detection or autoradiography. All microsatellites showed polymorphism and stable Mendelian inheritance. Differences in microsatellite variability between horse breeds were detected. A linkage analysis comprising HTG2-15, one coat colour gene and 16 genetic blood markers enabled addition of HTG2 to linkage group U2 and a new linkage group (U6) was established comprising the loci HTG7 and HTG12. Close linkage was excluded within a set of eight microsatellites. The estimated probability of exclusion in four breeds for a parentage test based on these eight loci varied between 0.96 and 0.99.