The Evolution of the Unusual Avian Microsatellite, Mme 12

The purpose of this study was to improve our understanding of the mutational processes that act upon microsatellite DNA Microsatellites are DNA sequences composed of tandem repeats of two to six nucleotide pairs. They are genetic markers that can be used in a wide range of studies including genetic mapping, population genetics, forensics, and parentage studies. Microsatellites evolve through mutation which changes the length of the allele. We chose to study the microsatellite Mme 12 because it has been known to amplify in a wide range of passerine species, and because it is a six base pair repeat (TGTGGG). Little is known about how this type of repeat may mutate. We determined the complete base-pair sequence of Mme 12 alleles from three out of the five different species of songbirds that were examined in this study. This experiment analyzed how these sequences at the Mme 12 locus differed between the species. We compared sequences of microsatellite DNA to determine whether mutations occurred in steps and whether small insertions/deletions were favored over large (greater than six base pairs) insertions/deletions. This study found that mutations did occur through stepwise mechanisms and that shorter insertions/deletions occurred more often than large ones