DEVELOPING BAC CONTIGS ON THE HORSE X CHROMOSOME

¹ Texas A&M University, 4458 TAMU, College Station, TX 77843-4458, USA

The X chromosome is the second largest chromosome in the equine genome with an estimated size of 153Mb. Very recently we generated a 169 marker 1Mb resolution map of this chromosome. These markers provide a powerful starting point to conduct detailed analysis in regions of interest along the chromosome. In an effort to initiate this, primers for individual markers are currently being used to screen the Texas A&M University and the CHORI-241 equine BAC libraries. Once BAC clones for all markers are obtained (currently BACs for 75 markers in hand), the work will focus on developing high resolution maps in 3 regions: the pseudoautosomal region located on the distal end of the short arm, the X-inactivation region located on the proximal end of the long arm, and the fragile X region located towards the distal end of the long arm. BAC clones from these regions will be end sequenced, and the sequence data will be used to develop primers for a stepwise chromosome walking in either direction. A map of overlapping BACs in the three regions will help to obtain a minimum tiling path that will provide essential details to expound upon our knowledge of these regions in the future. The assortment of remaining BACs along the length of the X chromosome will provide a starting point to analyze sex-linked disease traits in horses.