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Evaluation Guide for Coat Colors and Patterns

The genes for various colors and patterns are difficult to trace unless the colors are evaluated in a consistent, systematic way. The questions below can help guide the process. These questions provide additional information beyond what the handout Evaluating Dog Phenotypes does.

Detailed explanations of the loci involved and how the various pigments and regulators interact are provided in the Gene & Allele Summaries.

Question 1: does the dog have pure black or brown hairs anywhere in its coat?

Photo of german shepherd and yellow lab

This question evaluates activity of two loci: E (extension) and B (brown).

  • If a dog has pure black hairs in its coat (#1 above), it is producing the black pigment eumelanin.
    The dog is either genotype E/E or E/e (simple autosomal dominant)
  • If there are no black hairs, but chocolate brown hairs, the dog produces a brown version of eumelanin.
    That means it is homozygous recessive (bb) for the B locus.
  • The brown color still requires the dog to be either E/E, or E/e, so is an example of epistasis.
  • If there are no black or chocolate hairs in the coat, only yellow or red (#2 above), the dog is producing pheomelanin, but not eumelanin.
    Dogs that are red, yellow, or white (no black) are recessive (ee) at the E locus.
  • Caution: the black or brown pigment does not have to be in the entire length of the hair. The agouti locus (see Qu. 4-6 below) turns eumelanin deposition alternately on then off as the hair grows. In some dogs, only the tips of hairs will be black, or only the base. In both cases, the animal still is producing eumelanin, so must be E/- (E/E or E/e), and B/- (B/B or B/b).

Question 2: is the dog solid black (left) or brown (middle), or does it have other colors in its coat (right)?

Photos of black, chocolate, and yellow labs

This determines activity of the K (black) locus.

  • Dogs with patterned coats or agouti hairs must be recessive (k/k) for this locus.
    The simplest way to envision this locus is to imagine an autosomal dominant gene that increases eumelanin production and deposition to maximum levels, turning the entire dog black (E/-, B/-, K/-) or brown (E/-, b/b, K/-).

Question 3: is the color dark (#1 below), or does it look faded or bleached out (#2 below)?

Example of a normal colored versus a dilute colored Italian Greyhound

This assesses activity at the D (dilute) locus.
The D locus is much more obvious when it affects eumelanin. It can be difficult to detect in a dog with e/e genotype.

Question 4: are individual hairs banded with multiple colors (a below)?
Question 5: is the dog’s coat almost completely yellow or red (b below)?
Question 6: is there an obvious black-over-tan pattern (c below)?

Photos of dogs with an agouti coat, a yellow coat, and a black over tan coat

These three questions assess expression of various alleles of the A (agouti) locus.

Question 7: is the dog completely colored (a below) or does it have white in its coat (b and c below)?
Question 8: is it only found on the feet, tail tip, or as a chest star (b below), or does the white area include parts of the legs, chest, head, belly, back (c below)?

Photos of dogs with no white markings, a chest star, or white found throughout the body

Answers to these questions will determine the relative activity of the S (spotting) locus.

Question 9: does the dog have random, uneven mottled coloration of its coat (#1 below)?
Question 10: is one eye a different color than the other?

Photos of a non-merle and a merle border collie

These last two questions are assessing the M (merle) locus.

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Page last modified on Tuesday June 30, 2015 17:14:54 EDT

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