Isolation of subtelomeric DNA sequences labelling sheep and goat chromosome ends

Two techniques that make it possible to isolate telomere DNA are presented, using sheep as an example. The first technique is based upon the screening of a sheep BAC library with PCR amplified DNA segments preserved from high -power laser beam irradiation. Twenty-three BACs hybridising to 13 subtelom eric regions in sheep and goats were obtained (out of 27 in the sheep compl ement), of which 13 recognised more than one region, telomeric or not. Twen ty-three microsatellites were isolated from these BACs and 22 were genetica lly mapped on the sheep international genetic map, always consistently with the cytogenetical localisation in 17 cases out of 22. These results are di scussed. The second technique is based upon the selective cloning of subtel omeric enriched DNA. Preliminary results were obtained by this approach.