Low mutation rates of microsatellite loci in Drosophila melanogaster

Analysis of variation at microsatellite DNA loci is widely used in studies of parentage1, linkage2 and evolutionary history 3–5 . The utility of microsatel I ites is primarily due to high levels of allelic diversity, believed to reflect mutation rates orders of magnitude higher than base pair substitutions at single-copy genes. For humans 6–14 , mice 15–16 , rats 17 and pigs 18 , microsatellite mutation rates have been estimated at 10 −3 –10 −5 . However, a recent study comparing microsatellite variation in humans with non-human primates suggests that microsatellite mutation rates may vary considerably across taxa 19–20 . We measured mutation rates of 24 microsatellite loci in mutation accumulation lines of Drosophila melanogaster . Surprisingly, only a single mutation was detected after screening 157,680 allele-generations, yielding an estimated average mutation rate per locus of 6.3 × 10−6 , a mutation rate considerably lower than reported for various mammals. We propose that the comparatively low mutation rate is primarily a function of short microsatellite repeat lengths in the D. melanogaster genome.