THE HORSE KARYOTYPE, PHYSICAL MAP AND THE FUTURE

M.H. Gluck Equine Research Cente,r Department of Veterinary Science, University of Kentucky, Lexington, KY 40546 USA

Great strides have been made during the last three years with relation to the horse karyotype and physically mapped genetic markers. Both G-banded and R-banded karyotypes and ideograms have been standardized to aid researchers in identifying individual chromosomes. Human/horse homologies identified by chromosome painting have provided a base from which to begin the mapping of genes and other markers. The number of markers which have been physically mapped to horse chromosomes has increased from 7 to more than 100. Physically mapped markers anchor synteny and linkage groups to chromosomes. Although progress has been made, a few problems remain to be resolved. Laboratories around the world use different methods of chromosome preparation which may lead to subtle differences in banding patterns. Chromosome bands may vary between individual horses due to normal chromosome polymorphism. The resolution of chromosome painting is limited and may not identify small chromosome rearrangements. A suitable goal for 1999 would be to identify definitive markers for each chromosome which can used for physical mapping, linkage mapping and as reference probes for high resolution FISH mapping or gene ordering.