The application of AFLP fingerprinting to construct a YAC contig containing ADH2 and MTP on sheep chromosome 6

The low density of genetic markers on livestock maps limits progress in pos itional cloning projects. We demonstrate a strategy of combining comparativ e mapping with AFLP fingerprinting to develop physical maps in a defined re gion of the sheep genome. Sequence tagged sites for alcohol dehydrogenase 2 (ADH2) and microsomal triglyceride transfer protein (MTP) were developed a nd used to screen a sheep yeast artificial chromosome (YAC) library. Nine Y ACs were identified containing the microsatellite marker BM1329 and either ADH2 or MTP. Additional markers in the region were not available, and AFLP analysis was developed to identify sheep-specific bands within the YACs to determine their degree of overlap. Fourteen bands common to more than one Y AC were analysed and provided the markers necessary to develop a YAC contig containing the three STS markers. One YAC (yac260B5) containing all three markers (ADH2, MTP, and BM1329) was mapped to sheep chromosome 6q1.6 --> q1 .8 by FISH analysis.