UNEQUIVOCAL DETERMINATION OF SIRE ALLELE ORIGIN FOR MULTIALLELIC MICROSATELLITES WHEN ONLY THE SIRE AND PROGENY ARE GENOTYPED

The effect of a segregating economic trait locus (ETL) can be detected with the aid of a linked genetic marker, if specific alleles of each locus are in association among the individuals genotyped for the genet ic marker. For dairy cattle this can be achieved by application of the 'grand-daughter design'. If only the sires and their sons are genotyp ed for the genetic markers, then the allele origin of sons having the same genotypes as their sires cannot be determined. Seven sires and 1 0 1 sons were genotyped for five microsatellites. The mean frequency o f heterozygous sires was 77%. The mean number of alleles per locus was 8.2. Frequency of informative sons per locus ranged from 60% to 80% w ith a mean of 72%. With highly polymorphic microsatellites, at least 6 0% more grandsire families can be included in the analysis, and the nu mber of sons assayed can be reduced by 40%, as compared to diallelic m arkers.