Medycyna Wet. 68 (2), 74-78, 2012

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Stachurska A., Phaff Ussing A.
White markings in horses
White markings in horses result from the lack of melanocytes in the skin and hairs. The trait is characteristic of most breeds of domestic horses. In the breeding of the Polish Konik horse, which should resemble its wild ancestors, the lack of white markings was accepted as a selection criterion. The heritability of the markings is high. MC1R and ASIP loci, as well as two other putative QTLs are involved in the appearance of white markings. A foal should inherit a number of genes from both parents to make it possible for the markings to appear. The ultimate extent of markings is caused by the genes, as well as by intrauterine factors. The latter consist of accidental and random events which disturb the survival, migration and clonal proliferation of melanoblasts. The recessive e allele from MC1R locus and the dominant A allele from ASIP locus cause a greater extent of the markings, behaving as major genes. The most desired genotype of the Polish Konik horse, aaEEDD, which in inter se matings produces solely blue dun foals, is also the most desired with regard to the low amount of markings. To increase the progress in the Polish Konik breeding with regard to the absence of the markings, marked individuals and identified carriers of e allele should be consistently eliminated from reproduction.
Keywords: white markings, inheritance, horse