Diluted coat colors havemelanocytes, but vary from darker colors due to the concentration or type of these pigment-producing cells, not their absence. Pigment dilution, sometimes referred to as hypomelanism, has been called leucism, albinism (perfect, impartial, or dilute), ghosting, paling, and isabellinism.[1]
Albinism describes a condition where pigment cells synthesize little or no pigment
Leucism describes a condition that creates loss of pigment cells
In dogs, a mutation of theMLPH locus known as the dilute gene causes eumelanin to lighten while pheomelanin remains almost unchanged. Dogs of some breeds with the dilute gene often suffer fromcolour dilution alopecia (CDA).[2][3]
Of the colour shades found in thecoat of dogs, the light brown caused bypheomelanin is hardly affected. Blackeumelanin is lightened to a grey called "blue". Chocolate brown eumelanine is lightened to the typical colour of theWeimaraner.
Great Danes lightened from black to blue by the dilute gene.
Doberman: black with tan in the back, blue with tan in the front. The light brown areas were hardly lightened at all
The dilute gene d is recessive to thewild type allele D. A gene test can be used to determine a dog'sgenotype concerning genes for pigmentation. In somedog breeds lightened by the dilute gene, the mutation d is associated withcolor dilution alopecia (CDA). Since not all breeds in which the gene occurs exhibit these problems, it is suspected that there may be a second previously unknown mutation of the MLPH gene.[4][5][6][7]
DD: Both sire and dam have inherited the wild type allele. The coat is not lightened.
Dd: Either sire or dam have inherited theallele for dilution. However, the dilution of colour is not visible in thephenotype - the dog has the same coat colour as a DD dog.
dd: Sire and dam have inherited the allele for the dilute colour expression. The black areas of the coat are lightened to blue, dogs additionally lightened by the gene on theB locus take on the colour typical of the Weimaraner.
Cream gene, describes the process for horses by which the cremello, perlino, smoky cream double-dilute colors are created as well as thebuckskin,palomino and smoky black single dilute colors.
Dun gene describes another common dilution gene in horses
Champagne gene, describes a different dilution gene in horses that also creates cream coloring, pale skin with mottling and light-colored eyes.
Pearl gene, also called the "Barlink factor", is arecessive gene. One copy of the allele has no effect on the coat color of black, bay or chestnut horses. Two copies on a chestnut horse produce a pale, uniform apricot color of body hair, mane and tail as well as pale skin. It also interacts with Cream dilution to produce "pseudo-double" Cream dilutes with pale skin and blue or green eyes.
Silver Dapple Gene lightens black hair, such as the mane and tail of a bay horse
Mushroom (horse) describes an unknown and unmapped theorized dilution gene dilutes red pigment in body color to a pale beige color.
^Davis, Jeff N. (September–October 2007). "Color Abnormalities in Birds".Birding.39 (5). American Birding Association.
^Walser, Eva Holderegger (2019)."WELCHE FELLFARBEN KÖNNEN KRANK MACHEN?" [Which coat colours can make dogs sick?].Schweizer Hunde Magazin (in German). No. 8/19. pp. 12–17. Retrieved19 March 2024 – via Kynos Verlag.
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