Color Coded: DNA tests take much of the guesswork out of predicting coat color.
D. Caroline Coile, Ph.D.
If you breed Schipperkes or West Highland White Terriers, you probably don’t spend a lot of time questioning coat color in planned litters. But if you work with other breeds, you likely wonder what colors will result. And if you breed any of the breeds in which certain colors are disqualifying faults, you do more than wonder. You worry.
For the most part, coat color is far down the list of priorities when it comes to life-saving DNA testing. But color can make a difference in the disappointment a breeder will feel, the homes a dog will find, and in some cases, the health of the dog. DNA testing for color may seem frivolous, but for many breeders, it’s a precious tool.
In the following genetic-test descriptions, a locus is the location on the chromosome. Alleles are alternative forms of a gene. Uppercase letters designate dominant alleles; lowercase letters are used for recessive alleles.
B locus (black versus brown)
It all started with Labrador Retrievers. It seems simple enough. Labs can be yellow, black or chocolate. The guesswork came with yellow Labs. Breeders knew that chocolate was caused by the presence of two b alleles, but they couldn’t determine if a yellow Lab was BB (two dominant alleles), Bb (one dominant and one recessive allele) or bb (two recessive alleles). For that matter, they couldn’t tell whether a black dog was Bb or bb.
It wasn’t life-or-death knowledge, but with the number of Labs in the world, a DNA test for B versus b was certainly appreciated – and financially rewarding for breeders, who may have a greater demand for puppies of certain colors, and for the test manufacturers that provide these breeders with a test they want.
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