THE EXTENSION COAT COLOR LOCUS AND THE LOCI FOR BLOOD-GROUP-O AND TYROSINE AMINOTRANSFERASE ARE ON PIG CHROMOSOME-6

A linkage map of pig chromosome 6 was constructed using a wild pig/Lar ge White intercross pedigree, The map comprises 23 polymorphic loci, a nd the sex-average map length is similar to 170 cM, The study adds thr ee new genes to the chromosome 6 map: the extension (E) coat color loc us, and the blood group O (EAO) and tyrosine aminotransferase (TAT) lo ci, Segregation at the E locus determined two coat color phenotypes am ong the F-2 animals: wild-type color (El-) and black-spotting (E(p)/E( p)). The E locus showed close genetic linkage to the most distal marke r (S0035) on the short arm of chromosome 6, Comparative coat color gen etics as well as comparative mapping strongly suggest that E in pigs e ncodes the melanocyte-stimulating hormone receptor, as previously show n for the corresponding coat color loci in mouse and cattle, TAT was a lso mapped to the distal part of 6p, whereas EAO was the most distal m arker on 6q, A clear tendency for a higher recombination rate in both terminal regions was observed, A model for the evolution of pig chromo some 6, based on comparative mapping data, is presented.