Variation in Recombination Rate on BTA23: Fine Mapping and Construction of a YAC Contig

Abstract

To estimate the actual physical distance and to identify the putative DNA sequences responsible for variation in $\Theta$, a partial YAC contig was constructed for the D23S22-D23S23 interval. Primary screening of a YAC library yielded 17 YAC clones (sized from 180-2200 kb). For all YACs, YAC-end sequence rescue by inverse or vectorette PCR was used to develop 27 new STSs. All YAC ends were mapped using a somatic cell hybrid panel. The percentage of chimerism in this region was high (62%) in contrast to the previous estimate of 21% for this library. Estimation of the precise physical distance for the contig was not available due to a high proportion of clones being chimeric and to presence of two gaps in the contig. To correctly estimate the physical size of the interval and to complete the contig, additional YACs and/or BACs will be necessary. A correct order or loci between D23S22-D23S23 was determined on the basis of information from the contig: D23S23-D23S36-D23S7-VEGF-D23S22. Two new microsatellites on BTA23 were identified from the sequencing of YAC ends. These results provide a framework for determining the underlying molecular basis for variation in meiotic recombination rate.