January 11-15, 2003
Town & Country Convention Center
San Diego, CA
The dun phenotype in horses is characterized by coat color dilution of red and black pigments in body hair but not mane and tail hair. A darker dorsal stripe, as well as barring on the shoulder and leg, is often associated with dun. Dun is inherited as a dominant trait. The chromosome location of this locus has not yet been described. To map Dun, two Quarter Horse families segregating for the trait were screened using a genome scan comprised of 85 microsatellite markers spanning the 31 horse autosomes. The results of this scan demonstrated linkage of Dun to two markers on horse chromosome 8 (ECA8): ASB14 (RF = 0.18, LOD = 4.21) and LEX023 (RF = 0.17, LOD = 4.65). Chromosome specific analysis on a total of six Quarter Horse families confirmed the linkage of Dun to the group of ECA 8 markers: ASB14 (RF = 0.16, LOD = 6.65), COR003 (RF = 0.30, LOD = 4.58), COR012 (RF = 0.25, LOD = 7.68), LEX023 (RF = 0.19, LOD = 9.78), LEX029 (RF = 0.23, LOD = 9.68), UCDEQ46 (RF = 0.16, LOD = 14.54), UM034 (RF = 0.17, LOD = 10.31), UMNE70 (RF = 0.25, LOD = 4.57). Candidate genes for Dun have not yet been identified by comparative mapping analysis.