Dilution gene

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Two rats: left: agouti, right: coat lightened to blue by a dilution gene Rats - Dilution-Gene.jpg
Two rats: left: agouti, right: coat lightened to blue by a dilution gene

A dilution gene is any one of a number of genes that act to create a lighter coat color in living creatures. There are many examples of such genes:

Contents

General

Diluted coat colors have melanocytes, 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]

Cats

Cat coat genetics discusses many dilution genes in cats.

Dogs

In dogs, a mutation of the MLPH 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 from colour dilution alopecia (CDA). [2] [3]

Appearance

Of the colour shades found in the coat of dogs, the light brown caused by pheomelanin is hardly affected. Black eumelanin is lightened to a grey called "blue". Chocolate brown eumelanine is lightened to the typical colour of the Weimaraner.

Genetics

The dilute gene d is recessive to the wild type allele D. A gene test can be used to determine a dog's genotype concerning genes for pigmentation. In some dog breeds lightened by the dilute gene, the mutation d is associated with color 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]

Every dog has two alleles - one from the sire and one from the dam. The gene expression depends on the genotype:

Heredity diagram
Left: black eumelanin, right: brown eumelanin Dilution Gene - inheritance and effect.png
Heredity diagram
Left: black eumelanin, right: brown eumelanin
  1. DD: Both sire and dam have inherited the wild type allele. The coat is not lightened.
  2. Dd: Either sire or dam have inherited the allele for dilution. However, the dilution of colour is not visible in the phenotype - the dog has the same coat colour as a DD dog.
  3. 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 the B locus take on the colour typical of the Weimaraner.

According to the Mendelian Rules, an average of 25% of the puppies receive the homozygous gene combination dd if both parents are genetic carriers.

Horses

The effect of the champagne dilution gene on different horse coats. Dilution Gene - Champagne Horses.jpg
The effect of the champagne dilution gene on different horse coats.

Related Research Articles

<span class="mw-page-title-main">Cat coat genetics</span> Genetics responsible for the appearance of a cats fur

Cat coat genetics determine the coloration, pattern, length, and texture of feline fur. The variations among cat coats are physical properties and should not be confused with cat breeds. A cat may display the coat of a certain breed without actually being that breed. For example, a Neva Masquerade could wear point coloration, the stereotypical coat of a Siamese.

<span class="mw-page-title-main">Bay (horse)</span> Hair coat color of horses

Bay is a hair coat color of horses, characterized by a reddish-brown or brown body color with a black point coloration on the mane, tail, ear edges, and lower legs. Bay is one of the most common coat colors in many horse breeds.

At right is displayed the color traditionally called liver.

<span class="mw-page-title-main">Point coloration</span> Coloration of animal coat/fur

Point coloration is animal coat coloration with a pale body and relatively darker extremities, i.e. the face, ears, feet, tail, and scrotum. It is most recognized as the coloration of Siamese and related breeds of cat, but can be found in dogs, rabbits, rats, sheep, guinea pigs and horses as well.

<span class="mw-page-title-main">Gray horse</span> Coat color characterized by progressive depigmentation of the colored hairs of the coat

A gray horse has a coat color characterized by progressive depigmentation of the colored hairs of the coat. Most gray horses have black skin and dark eyes; unlike some equine dilution genes and some other genes that lead to depigmentation, gray does not affect skin or eye color. Gray horses may be born any base color, depending on other color genes present. White hairs begin to appear at or shortly after birth and become progressively more prevalent as the horse ages as white hairs become intermingled with hairs of other colors. Graying can occur at different rates—very quickly on one horse and very slowly on another. As adults, most gray horses eventually become completely white, though some retain intermixed light and dark hairs.

<span class="mw-page-title-main">Cream gene</span> Gene for several horse coat colors

The cream gene is responsible for a number of horse coat colors. Horses that have the cream gene in addition to a base coat color that is chestnut will become palomino if they are heterozygous, having one copy of the cream gene, or cremello, if they are homozygous. Similarly, horses with a bay base coat and the cream gene will be buckskin or perlino. A black base coat with the cream gene becomes the not-always-recognized smoky black or a smoky cream. Cream horses, even those with blue eyes, are not white horses. Dilution coloring is also not related to any of the white spotting patterns.

<span class="mw-page-title-main">Champagne gene</span> Simple dominant allele responsible for a number of rare horse coat colors

The champagne gene is a simple dominant allele responsible for a number of rare horse coat colors. The most distinctive traits of horses with the champagne gene are the hazel eyes and pinkish, freckled skin, which are bright blue and bright pink at birth, respectively. The coat color is also affected: any hairs that would have been red are gold, and any hairs that would have been black are chocolate brown. If a horse inherits the champagne gene from either or both parents, a coat that would otherwise be chestnut is instead gold champagne, with bay corresponding to amber champagne, seal brown to sable champagne, and black to classic champagne. A horse must have at least one champagne parent to inherit the champagne gene, for which there is now a DNA test.

<span class="mw-page-title-main">Silver dapple gene</span>

The silver or silver dapple (Z) gene is a dilution gene that affects the black base coat color and is associated with Multiple Congenital Ocular Abnormalities. It will typically dilute a black mane and tail to a silvery gray or flaxen color, and a black body to a chocolaty brown, sometimes with dapples. It is responsible for a group of coat colors in horses called "silver dapple" in the west, or "taffy" in Australia. The most common colors in this category are black silver and bay silver, referring to the respective underlying coat color.

<span class="mw-page-title-main">Equine coat color genetics</span> Genetics behind the equine coat color

Equine coat color genetics determine a horse's coat color. Many colors are possible, but all variations are produced by changes in only a few genes. Bay is the most common color of horse, followed by black and chestnut. A change at the agouti locus is capable of turning bay to black, while a mutation at the extension locus can turn bay or black to chestnut.

<span class="mw-page-title-main">Dun gene</span> Dilution gene

The dun gene is a dilution gene that affects both red and black pigments in the coat color of a horse. The dun gene lightens most of the body while leaving the mane, tail, legs, and primitive markings the shade of the undiluted base coat color. A dun horse always has a dark dorsal stripe down the middle of its back, usually has a darker face and legs, and may have transverse striping across the shoulders or horizontal striping on the back of the forelegs. Body color depends on the underlying coat color genetics. A classic "bay dun" is a gray-gold or tan, characterized by a body color ranging from sandy yellow to reddish brown. Duns with a chestnut base may appear a light tan shade, and those with black base coloration are a smoky gray. Manes, tails, primitive markings, and other dark areas are usually the shade of the undiluted base coat color. The dun gene may interact with all other coat color alleles.

<span class="mw-page-title-main">Chestnut (horse color)</span> Horse coat color

Chestnut is a hair coat color of horses consisting of a reddish-to-brown coat with a mane and tail the same or lighter in color than the coat. Chestnut is characterized by the absolute absence of true black hairs. It is one of the most common horse coat colors, seen in almost every breed of horse.

Follicular dysplasia is a genetic disease of dogs causing alopecia, also called hair loss. It is caused by hair follicles that are misfunctioning due to structural abnormality. There are several types, some affecting only certain breeds. Diagnosis is achieved through a biopsy, and treatment is rarely successful. Certain breeds, such as the Mexican Hairless Dog and Chinese Crested Dog, are bred specifically for alopecia.

<span class="mw-page-title-main">Equine coat color</span> Horse coat colors and markings

Horses exhibit a diverse array of coat colors and distinctive markings. A specialized vocabulary has evolved to describe them.

<span class="mw-page-title-main">White horse</span> Horse coat color

A white horse is born predominantly white and stays white throughout its life. A white horse has mostly pink skin under its hair coat, and may have brown, blue, or hazel eyes. "True white" horses, especially those that carry one of the dominant white (W) genes, are rare. Most horses that are commonly referred to as "white" are actually "gray" horses whose hair coats are completely white. Gray horses may be born of any color and their hairs gradually turn white as time goes by and take on a white appearance. Nearly all gray horses have dark skin, except under any white markings present at birth. Skin color is the most common method for an observer to distinguish between mature white and gray horses.

<span class="mw-page-title-main">Melanophilin</span> Protein-coding gene in the species Homo sapiens

Melanophilin is a carrier protein which in humans is encoded by the MLPH gene. Several alternatively spliced transcript variants of this gene have been described, but the full-length nature of some of these variants has not been determined.

<span class="mw-page-title-main">Labrador Retriever coat colour genetics</span> Genetics behind Labrador Retriever coat colour

The genetic basis of coat colour in the Labrador Retriever has been found to depend on several distinct genes. The interplay among these genes is used as an example of epistasis.

<span class="mw-page-title-main">Pearl gene</span> Type of dilution gene

The Pearl gene, also known as the "Barlink factor", is a dilution gene at the same locus as the cream gene, which somewhat resembles the cream gene and the champagne gene but is unrelated to champagne. It is a somewhat rare dilution gene found in the American Quarter Horse, American Paint Horse, and Peruvian Paso. The same mutation appears in Iberian horse breeds such as the Lusitano and Andalusian. The existence of the pearl gene in Quarter Horses and Paints is probably because these breeds have some Iberian ancestors.

<span class="mw-page-title-main">Lavender (chicken plumage)</span>

Lavender or self-blue refers to a plumage color pattern in the chicken characterized by a uniform, pale bluish grey color across all feathers. The distinctive color is caused by the action of an autosomal recessive gene, commonly designated as "lav", which reduces the expression of eumelanin and phaeomelanin so that black areas of the plumage appear pale grey instead, and red areas appear a pale buff.

<span class="mw-page-title-main">Mushroom gene</span>

Identified in 2014, the mushroom gene is a recessive dilution gene that affects red pigment in horses.

<span class="mw-page-title-main">Dog coat genetics</span> Genetics behind dog coat

Dogs have a wide range of coat colors, patterns, textures and lengths. Dog coat color is governed by how genes are passed from dogs to their puppies and how those genes are expressed in each dog. Dogs have about 19,000 genes in their genome but only a handful affect the physical variations in their coats. Most genes come in pairs, one being from the dog's mother and one being from its father. Genes of interest have more than one expression of an allele. Usually only one, or a small number of alleles exist for each gene. In any one gene locus a dog will either be homozygous where the gene is made of two identical alleles or heterozygous where the gene is made of two different alleles.

References

  1. Davis, Jeff N. (September–October 2007). "Color Abnormalities in Birds". Birding. 39 (5). American Birding Association.
  2. 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. Retrieved 19 March 2024 via Kynos Verlag.
  3. Philipp, Ute; Hamann, Henning; Mecklenburg, Lars; Nishino, Seiji; Mignot, Emmanuel; Günzel-Apel, Anne-Rose; Schmutz, Sheila M.; Leeb, Tosso (2005). "Polymorphisms within the canine MLPH gene are associated with dilute coat color in dogs". BMC Genetics. 6: 34. doi: 10.1186/1471-2156-6-34 . PMC   1183202 . PMID   15960853. Art. No. 34.
  4. Ute Philipp, Henning Hamann, Sheila Schmutz et al.: within the canine MLPH gene are associated with dilute coat color in dogs . In: BMC Genetcs, 2005.
  5. U. Philipp, P. Quignon, A. Scott, C. Andre, M. Breen, T. Leeb: Chromosomal assignment of the canine melanophilin gene (MLPH): a candidate gene for coat color dilution in Pinschers . In: J Hered. 96(7), 2005, page 774–776. June 15, 2005.
  6. C. Drogemuller, U. Philipp, B. Haase, A. R. Gunzel-Apel, T. Leeb: A noncoding melanophilin gene (MLPH) SNP at the splice donor of exon 1 represents a candidate causal mutation for coat color dilution in dogs . In: J Hered. 2007.
  7. Samantha L. van Buren, Katie L. Minor et al.: A Third MLPH Variant Causing Coat Color Dilution in Dogs . In: Genes, Vol. 11, Issue 6, June 2020.

See also