HETEROGENEITY IN RATES OF RECOMBINATION ACROSS THE MOUSE GENOME

If loci are randomly distributed on a physical map, the density of mar kers on a genetic map will be inversely proportional to recombination rate. First proposed by MARY LYON, We have used this idea to estimate recombination rates from the Drosophila melanogaster linkage map. Thes e results were compared with results of two other studies that estimat ed regional recombination rates in D. melanogaster using both physical and genetic maps. The three methods were largely concordant in identi fying large-scale genomic patterns of recombination. The marker densit y method was then applied to the Mus musculus microsatellite linkage m ap. The distribution of microsatellites provided evidence for heteroge neity in recombination rates. Centromeric regions for several mouse ch romosomes had significantly greater numbers of markers than expected, suggesting that recombination rates were lower in these regions. In co ntrast, most telomeric regions contained significantly fewer markers t han expected. This indicates that recombination rates are elevated at the telomeres of many mouse chromosomes and is consistent with a compa rison of the genetic and cytogenetic maps in these regions. The densit y of markers on a genetic map may provide a generally useful way to es timate regional recombination rates in species for which genetic, but not physical, maps are available.