The source of the COPA gene traces back to a cow born in Canada in 1980. As the name suggests, the COPA gene can supersede the MCR1 genotype and be the sole determining factor for coat color. This means that animals that inherit one copy of the COPA red, known as the Dominant Red or Variant-Red allele, from either parent will exhibit a red and white phenotype, regardless of their genotype for the MCR1 gene.
New-release sire, 250HO16428 LUCKY SEVEN-RED, has a red and white phenotype due to being heterozygous for the COPA gene, meaning he has one copy of the Dominant Red allele and one copy of the wild-type allele. This is reflected with a code of DR1, which is listed as part of his genetic condition results in Select Sires’ publications and in official Holstein Association records. For the MCR1 gene, LUCKY SEVEN-RED has two copies of the dominant black allele, which would otherwise suggest black coat color if the COPA gene wasn’t present. Because he is heterozygous for the COPA gene, 50% of LUCKY SEVEN-RED’s offspring are expected to have a red and white phenotype, regardless of the coat color of the dam. For example, if LUCKY SEVEN-RED is mated to a red and white cow who had two copies of the recessive red allele for the MCR1 gene, we’d expect 50% of the offspring to have black and white phenotypes – these animals did not inherit the dominant red allele of the COPA gene from LUCKY SEVEN-RED. We’d also expect 50% of the offspring to have red and white phenotypes – these animals did inherit the dominant red allele of the COPA gene from LUCKY SEVEN-RED. In this scenario, 100% of the offspring would be expected to be heterozygous at the MCR1 site, or red carriers. Similarly, if LUCKY SEVEN-RED was mated to a black and white cow, who had no copies of the red allele at the MCR1 site, we’d still expect 50% of the calves to have a red and white phenotype.
There are genetic tests available for this condition through CLARIFIDE® testing at Zoetis and from the Veterinary Genetics Laboratory at UC-Davis.
Here’s an explanation of potential test results from UC-Davis:
Alleles: N = No Dominant Red, DR = Dominant Red
| TEST RESULT | DOMINANT RED STATUS |
|---|
| N/N | No copies of Dominant Red present. Color is dependent on MC1R genotype. |
| N/DR | 1 copy of Dominant Red present. Animal is red and white and 50% of offspring are expected to be red and white. |
| DR/DR | 2 copies of Dominant Red present. Animal is red and white; all offspring are expected to be red and white. |
More information can be found in these factsheets from Zoetis and UC-Davis.