Mutations in sheep microsatellites.

During the construction of a primary linkage map of the sheep genome, a total of 46,225 parent-offspring transfer of microsatellite alleles were examined through the genotyping of the AgResearch International Mapping Flock. Any observations of mutations were thoroughly rechecked, including examination of new DNA samples, to yield five bona fide mutations from the study. This gave us an observed spontaneous mutation rate for microsatellites in sheep of 1.1 +/- 0.5 x 10(-4) mutations/gamete per locus. Untransformed lymphocytes were used as the source of DNA. Two of the mutations could have happened at either meiosis or during mitotic growth of the male germ cells. The other three mutations probably occurred early in the mitotic generation of the female germ cells. All of the mutations consisted of a 2-bp insertion and occurred in individuals heterozygous at the mutant locus.