MUTATION-RATE IN HUMAN MICROSATELLITES - INFLUENCE OF THE STRUCTURE AND LENGTH OF THE TANDEM REPEAT

In 10,844 parent/child allelic transfers at nine short-tandem-repeat ( STR) loci, 23 isolated STR mismatches were observed. The parenthood in each of these cases was highly validated (probability >99.97%). The e vent was always repeal related, owing to either a single-step mutation (n = 22) or a double-step mutation (n = 1). The mutation rate was bet ween 0 and 7 x 10(-3) per locus per gamete per generation. No mutation s were observed in three of the nine Loci. Mutation events in the male germ line were five to six times more frequent than in the female ger m line. A positive exponential correlation between the geometric mean of the number of uninterrupted repeats and the mutation rate was obser ved. Our data demonstrate that mutation rates of different loci can di ffer by several orders of magnitude and that different alleles at one locus exhibit different mutation rates.