One locus is involved, and can bear only two allels:
Allel E -> let the eumelanin express itself, which giveslivercolor.
Allel e -> let the phaeomelanin express itself, which gives thefawncolor. This allel is said to be "epistatic", which means that it masks the effect of another gene, in this case the gene giving the liver color on the hairs. Example of another well known epistatic gene: the gene giving albinism which prevent any color to appear all over the body.
The allel E is dominant compared to allel e.
We have 3 possible genotypes, giving 2 phenotypes. Infawn the fawn dogs, inliver the liver dogs:
|
Genotype |
Phenotype |
|
e-e |
Fawn |
|
e-E |
Liver |
|
E-E |
Liver |
|
e |
e |
|
|
e |
e-e |
e-e |
|
e |
e-e |
e-e |
Expected litter: 100% ofe-e(Fawn)
|
e |
E |
|
|
e |
e-e |
e-E |
|
e |
e-e |
e-E |
Expected litter: 50% ofe-e(Fawn) and 50% of e-E(Liver)
|
E |
E |
|
|
e |
e-E |
e-E |
|
e |
e-E |
e-E |
Expected litter: 100% ofe-E(Liver)
|
e |
E |
|
|
e |
e-e |
e-E |
|
E |
e-E |
E-E |
Expected litter: 25% ofe-e(Fawn), 50% of e-E(Liver) and 25% of E-E(Liver)
|
E |
E |
|
|
e |
e-E |
e-E |
|
E |
E-E |
E-E |
Expected litter: 50% ofe-E(Liver), 50% of E-E(Liver)
|
E |
E |
|
|
E |
E-E |
E-E |
|
E |
E-E |
E-E |
Expected litter: 100% ofE-E(Liver)