---
title: "7.4.1 Color genes in ruminants"
canonical: "https://wiki.groenkennisnet.nl/space/TAB/296681546/7.4.1%20Color%20genes%20in%20ruminants"
format: markdown
---
In ruminants, as in all mammals, four genes determine the colour of the coat: the Extension, Agouti, Roan and the dilution gene.

The *extension gene* determines the pigment colour of an animal. The dominant allele E is responsible for the production of eumenalin in coat cells of black animals and the recessive allele e for phaeomelanin responsible the red colour in animals. A third allele is responsible for the wild phenotype (red with a light backline).

![image](media://9121e976-d5ce-4450-95dc-2febd59646a9)

The *agouti* gene is expressed when at the E locus at least one wild allele is present. It is an example of epistatis: the genotype on the extension locus determines the expression of alleles on the agouti locus. The agouti alleles give a striping pattern of black and red.

  

![image](media://846f3e99-b689-44a7-9d70-9e05e34f4a27)

A dominant allele at the roan locus is responsible for the presence of white and colored hairs next to each other. It leads to a grey color of the animals. 

    

![image](media://ec73defa-cfa0-41ff-9563-85970b363ec2)

  

The dilution gene dilutes, when the dominant allele is homozygous, the base color very much. In case of a black animal, the homozygous animals give light grey patterns. The heterozygous animals have dark grey patterns. 

Figure 4: a white grey calf of the Danish Heath Breed imported in The Netherlands (left) and a Dutch “Witrik” (color sided) cow with the dark grey pattern

In cattle, sheep and goat white spots may be present caused by several known loci: the spotting, blaze, belting, color sided and brockling loci. For further information see e.g. : The genetics of cattle, 1999. Editors R. Fries and A. Ruvinsky, and The genetics of sheep, 1997. Editors L.Piper and A. Ruvinsky.

> Macro (children)