* Roan cattle are a result of a specific pattern of inheritance for coat color.
* The gene: There's a single gene responsible for coat color, with two alleles (versions of the gene):
* R: Allele for red coat color.
* W: Allele for white coat color.
* Codominance: In roan cattle, the R and W alleles are codominant. This means that when both alleles are present, they both express themselves equally, resulting in a mixture of red and white hairs.
* Possible Genotypes and Phenotypes:
* RR: Red coat (homozygous for red)
* WW: White coat (homozygous for white)
* RW: Roan coat (heterozygous)
Let's break down the offspring ratios you mentioned:
* 25% Red: This arises from the mating of two roan cattle (RW x RW). 25% of the offspring will inherit both R alleles (RR) and thus have a red coat.
* 50% Roan: The majority of the offspring (50%) inherit one R and one W allele (RW), resulting in the roan coat.
* 25% White: 25% of the offspring inherit both W alleles (WW) and thus have a white coat.
The Observation of White and Red Hairs:
The reason you see both white and red hairs on a roan cow is because the R and W alleles are expressed simultaneously in each individual hair follicle. This results in the blended appearance of roan.
In Summary:
Roan cattle demonstrate codominance, where both alleles of a gene are expressed equally, leading to a unique blended phenotype.