BROWN COAT COLOR IN ICELANDIC CATTLE PRODUCED BY THE LOCI EXTENSION AND AGOUTI

Inheritance of the colors black, brown, and red in Icelandic cattle wa s studied. The three colors are produced by two loci, Extension (E) an d Agouti (A), with three alleles at the E locus: E(d) for dominant bla ck, E(+), intermediate, which allows expression of A locus alleles; an d e for recessive red color. Two alleles are postulated at the A locus : A(+), producing brown, and a, producing recessive black (nonagouti) when homozygous in E(+)/- animals. The dominant and recessive types of black are indistinguishable from each other phenotypically. The A all eles are only able to express their effect in E(+)/- genotypes. The E and A loci in cattle are postulated to be homologous to the E and A lo ci in the mouse.