ON THE GENETICS OF POINT AND BODY COLORS IN HORSES - IN COMPARISON TOMOLECULAR ANALYSES OF COLOR LOCI IN MICE

SEARLE (1968) listed in ''Comparative Genetics of Coat Colour in Mamma ls'' for horses the following polymorphic loci: A, B, C, D, E, G, R, S (Z) and W. In mice the loci a, b, c, e and d have been identified, lo calized and characterized on the molecular level. The consequences of these results in mice on colour genetics in horses are discussed. The conclusions of ADALSTEINSSON (1974), ANDERSSON and SANDBERG (1987), th at chestnut/sorrel colours are caused by the recessive genotype at the E-Locus rather than by the B-Locus are in good agreement with molecul ar genetic results at the respective loci in mice. This good agreement also holds true for allels at the A, B and E Loci which determine bla ck colours as well. Blacks have the genotypes aa B-EE or aa B-Ee and j et blacks--B-E(d)-. The correlations to Loci assumed to be responsible for colour dilutions C, D and Z are also of interest. By comparative mapping, the homologies between horses and other mammalian species can be shown. It is concluded that identification, localization and chara cterization of colour loci in horses is of great interest for horse br eeding. Since experimental crosses in horses are too expensive, the in formative families necessary for comparative mapping have to be establ ished in herdbook populations. International standardized colour descr iption systems and the complete registration of the colours of horses are necessary for this pulpose. Since genetic defects and reduced resi stance against diseases can be caused by pleiotropic effects of colour genes, horse colour genetics is of economic and ethical importance.