Lavender or self-blue refers to a plumage color pattern in the chicken (Gallus gallus domesticus) 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. [1]
The "lavender" gene (lav) in the chicken causes the dilution of both black (eumelanin) and red/brown (phaeomelanin) pigments, so according to color background, dilution due to "lavender" gives a sort of plumage color patterns: On an extended black background, this condition causes the entire surface of the body an even shade of light slaty blue, which is the typical phenotype known as '"self-blue"'.
On a red/brown color plumage background, lavender gene degrades color to beige, like in some Pekin Bantams as in the picture set aside. On the color background of the Belgian Bearded d'Uccle Bantams, frequently referred to as the "Mille Fleur" in the United States, [2] lavender causes the pattern known as "porcelain". The resulting "porcelain" pattern is beige with each feather tipped with a V-shaped of slaty blue near the end of the feather and the feather tipped with a V-shaped white spangle. [3]
Light and electron microscope studies have revealed that, although lavender melanocytes possess relatively normal dendrite morphology, there is defective peripheral accumulation of melanosomes to the dendrites. [4] This results in the patchy transfer of melanosomes into the keratinocytes of the growing feather. The dilution effect is essentially the result of a mixture of pigmented and unpigmented regions within the feather barbs.
The lavender gene was first discovered in the Porcelain variety of Belgian Bearded d'Uccle bantams in 1972, [5] and verified in 1980. [1] Porcelain colored d'Uccle bantams were around as early as 1909, [6] [7] though the Porcelain variety was not recognized by the American Poultry Association until 1964. [8] Whether from the Porcelain d'Uccle or other, unknown sources, the lavender gene has been introduced to a number of new chicken breeds over the years, including the Polish and the Silkie.
"Lavender" is an autosomal recessive mutation of the chicken affecting the neural crest derived melanocytes. It causes the dilution of both eumelanin and phaeomelanin to a light grey or buff, respectively. It has been assigned the symbol lav. [5] [9]
The ultimate goal of the modern genetic studies is to find out the underlying genes involved in these traits. Lavender in chickens has been found to be a mutation caused by a single base-pair change in exon 1 of MLPH (melanophilin) gene. [10]
In genetic linkage studies, Lav locus has been assigned to a linkage group known as Cp-R-U group (Creeper-Rose comb-Uropygial) . Although Lavender locus is linked to the R (rose comb) locus by 32.5%, its position has not yet mapped., [11]
Until now, all the reported causal mutations in MLPH (melanophilin) of humans, mice and other species have been single-base substitutions or small deletions, the effects of which were limited to the dilution of hair [12] [13] or feather colour. [10] The MLPH-associated dilution of coat or plumage pigmentation should then result in the defective transport of melanosomes. This produces a diluted, leaden or lavender blue-grey colour and has been reported in several mammals: humans (Griscelli syndrome type 3), [12] mice, [14] cats, [15] dogs [16] and minks [17]
The lavender phenotype in Japanese quail (Coturnix coturnix japonica) is a dilution of both eumelanin and phaeomelanin in feathers that produces a blue-grey colour on a wild-type feather pattern background. Studies of intergeneric hybridization proved that the lavender mutation in quail is homologous to the same phenotype in chicken [18]
In this species, the lavender phenotype is associated with a non-lethal complex mutation involving three consecutive overlapping chromosomal changes (two inversions and one deletion) that have consequences on the genomic organization of four genes (MLPH and the neighbouring PRLH, RAB17 and LRRFIP1). The deletion of PRLH has no effect on the level of circulating prolactin. Lavender birds have lighter body weight, lower body temperature and increased feed consumption and residual feed intake than wild-type plumage quail, indicating that this complex mutation is affecting the metabolism and the regulation of homeothermy. [19]
In other bird species, similar feather colour dilutions have been described, including the autosomal recessive slate turkey ( Meleagris gallopavo ), [9] [20] milky pigeon ( Columba livia ), [21] and the lavender muscovy duck ( Cairina moschata ). [22] It is as yet unknown which genes are responsible for these dilution mutations in these bird species.
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:
Cat coat genetics determine the coloration, pattern, length, and texture of feline fur. Understanding how can be challenging because many genes are involved. 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 Siberian could wear point coloration, the stereotypical coat of a Siamese.
Plumage is a layer of feathers that cover a bird and the pattern, colour, and arrangement of those feathers. The pattern and colours of plumage differ between species and subspecies and may vary with age classes. Within species, there can be different colour morphs. The placement of feathers on a bird is not haphazard, but rather emerge in organized, overlapping rows and groups, and these feather tracts are known by standardized names.
At right is displayed the color traditionally called liver.
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.
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. The "base" colors of the horse are determined by the Extension locus, which in recessive form (e) creates a solid chestnut or "red" coat. When dominant (E), a horse is black. The next gene that strongly affects coat color, Agouti, when present on a horse dominant for E, limits the black color to the points, creating a shade known as Bay that is so common and dominant in horses that it is informally grouped as a "base" coat color.
The science of budgerigar color genetics deals with the heredity of mutations which cause color variation in the feathers of the species known scientifically as Melopsittacus undulatus. Birds of this species are commonly known by the terms 'budgerigar', or informally just 'budgie'.
The Barbu d'Uccle or Belgian d'Uccle, Dutch: Ukkelse Baardkriel, is a Belgian breed of bearded bantam chicken. It was first bred in the town of Uccle on the outskirts of Brussels, in central Belgium, in the early years of the twentieth century. It is a true bantam, with no standard-sized large fowl counterpart, and is one of eleven Belgian true bantam breeds.
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.
Unconventional myosin-Va is a motor protein in charge of the intracellular transport of vesicles, organelles and protein complexes along the actin filaments. In humans it is coded for by the MYO5A gene.
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.
The Booted Bantam or Dutch Booted Bantam is a European breed of true bantam chicken. It is characterised by abundant feathering on the feet and shanks, which gives it a "booted" appearance; and by vulture hocks, long stiff downward-pointing feathers on backs of the thighs, from which the Dutch name Sabelpoot ("sabre-legged") derives.
The science of cockatiel colour genetics deals with the heredity of colour variation in the feathers of cockatiels, Nymphicus hollandicus. Colour mutations are a natural but very rare phenomenon that occur in either captivity or the wild. About fifteen primary colour mutations have been established in the species which enable the production of many different combinations. Note that this article is heavily based on the captive or companion cockatiel rather than the wild cockatiel species.
Amelanism is a pigmentation abnormality characterized by the lack of pigments called melanins, commonly associated with a genetic loss of tyrosinase function. Amelanism can affect fish, amphibians, reptiles, birds, and mammals including humans. The appearance of an amelanistic animal depends on the remaining non-melanin pigments. The opposite of amelanism is melanism, a higher percentage of melanin.
The melanocortin 1 receptor (MC1R), also known as melanocyte-stimulating hormone receptor (MSHR), melanin-activating peptide receptor, or melanotropin receptor, is a G protein–coupled receptor that binds to a class of pituitary peptide hormones known as the melanocortins, which include adrenocorticotropic hormone (ACTH) and the different forms of melanocyte-stimulating hormone (MSH). It is coupled to Gαs and upregulates levels of cAMP by activating adenylyl cyclase in cells expressing this receptor. It is normally expressed in skin and melanocytes, and to a lesser degree in periaqueductal gray matter, astrocytes and leukocytes. In skin cancer, MC1R is highly expressed in melanomas but not carcinomas.
Solid black plumage color refers to a plumage pattern in chickens characterized by a uniform, black color across all feathers. There are chicken breeds where the typical plumage color is black, such as Australorp, Sumatra, White-Faced Black Spanish, Jersey Giant and others. And there are many other breeds having different color varieties, which also have an extended black variety, such as Leghorn, Minorca, Wyandotte, Orpington, Langshan and others.
In poultry standards, solid white is coloration of plumage in chickens characterized by a uniform pure white color across all feathers, which is not generally associated with depigmentation in any other part of the body.
The Frizzle is a breed of chicken with characteristic curled or frizzled plumage. While the frizzle gene can be seen in many breeds, such as the Pekin and Polish, the Frizzle is recognised as a distinct breed in a number of European countries and Australia. In the United States frizzled chickens are not considered a breed, and at shows are judged by the standards of the breed they belong to.
Sex-linked barring is a plumage pattern on individual feathers in chickens, which is characterized by alternating pigmented and apigmented bars. The pigmented bar can either contain red pigment (phaeomelanin) or black pigment (eumelanin) whereas the apigmented bar is always white. The locus is therefore often referred to as an ‘eumelanin diluter’ or ‘melanin disruptor’. Typical sex-linked barred breeds include the Barred Plymouth Rock, Delaware, Old English Crele Games as well as Coucou de Renne.
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