How do I know if my black cow/bull is homozygous black?

In order to know if a black animal is homozygous black, you need to either DNA test for coat color on that animal or have documentation that both parents tested homozygous black. Black coat color is a dominant trait and will mask the presence of other coat color alleles. The gene that controls the distinction between black, wild type, and red coat color is called the extension locus. There are three alleles (variations) for this gene in cattle: black (ED), wild type (E+), or red (Ed). The black variation is dominant to both wild type and red. The wild type allele is dominant to red. Black animals can have three different genotypes for coat color: ED/ED (homozygous black), ED/E+, or ED/Ed (the latter two are heterozygous). Therefore, black animals can pass on the wild type or red allele to the next generation and have wild type or red calves. Conversely, as red is a recessive trait, red animals will always be Ed/Ed and will always pass on the red allele to their calves.

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