Abstract for presentation at 11th International Congress of Human Genetics

Microsatellites have become the DNA marker of choice for a wide range of biological investigations, but the mechanisms that contribute to microsatellite variation are poorly understood. Although replication slippage is considered the predominant mechanism by which mutations are generated, the role of other mechanisms related to DNA recombination is unclear. A better understanding of microsatellite evolution is essential to fully utilise these important molecular markers. In marsupials, unlike eutherian mammals, the Y chromosome does not undergo any recombination, while the X chromosome can recombine in XX females but not in XY males. Consequently, we can compare microsatellites from the different chromosomes to partition the effects of recombinant and non-recombinant classes of mutation. We have developed a suite of 30 novel microsatellites from tammar wallaby (Macropus eugenii) BAC clones. Ten microsatellites originate from the Y chromosome, nine from the X chromosome and 11 from chromosome 2. We are comparing allele numbers and frequencies among several hundred wallabies sampled from Kangaroo and Garden Islands to determine whether there are substantive differences in allelic diversity between the chromosomes. These data may shed light on the different mutational mechanisms acting on these microsatellites as a consequence of their chromosomal location. Small-pool PCR from sperm samples will also be explored as a method to identify germline mutations within individual males. The results of this research will be of relevance to all vertebrate studies that utilise microsatellite markers. In addition, the sex chromosome markers developed may provide new insights to population studies of the tammar wallaby and a range of related species.