A specific type of melanin called eumelanin creates a dark skin tone; the more eumelanin your body produces, the darker your skin will be.
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Our bodies create two types of melanin called eumelanin and pheomelanin.
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But eumelanin isn't the only pigment of interest to the scientists.
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For the color red, the version of melanin is pheomelanin, and for the color black it's eumelanin.
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As it turned out, MFSD12 can affect the production of brown-black eumelanin, producing a darker skin color.
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Image: University of GӧttingenPrior to the new study, scientists had already developed a technique for detecting eumelanin in ancient fossils.
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"In mammals and other animals there are two types of melanin, the brownish black eumelanin and the reddish pheomelanin," Bergmann said.
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If your MC1R gene is working as it should, your body will produce more eumelanin, which results in darker hair and skin.
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They found traces of the pigment eumelanin, responsible for the brown eyes and dark hair found in many modern species, including humans.
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Eumelanin also absorbs the ultraviolet light hitting the skin, turning it into heat to protect the body's DNA from the rays' damaging effects.
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But the real breakthrough emerged when the researchers identified traces of a pigment called eumelanin in both the fossil insects and living crane flies.
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That's the preferred tactic of this research group, which previously found evidence of eumelanin — a brown and black pigment — in the plumage of the feathered dinosaur Archaeopteryx.
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So, redheads have a version of a gene called MC1R that causes melanocytes to produce more of the pheomelanin, rather than the eumelanin—as a result, they have paler skin and the signature red hair.
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Melanin-producing cells, called melanocytes, create not one, but two classes of melanin—pheomelanins, which produces yellow and red hair and all the pink parts of your body like your lips and your genitals, and eumelanin, which produces the darker colors.
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Three years ago, Nick Edwards, a co-author of the new study and a scientist at SLAC National Accelerator Laboratory, showed that it was possible to distinguish eumelanin pigments from pheomelanin pigments in modern birds, a discovery that established important groundwork for the new study.
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There are two types of eumelanin, which are brown eumelanin and black eumelanin. Those two types of eumelanin chemically differ from each other in their pattern of polymeric bonds. A small amount of black eumelanin in the absence of other pigments causes grey hair. A small amount of brown eumelanin in the absence of other pigments causes yellow (blond) hair.
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The pigment eumelanin gives brown hair its distinctive color. Brown hair has more eumelanin than blond hair but also has far less than black. There are two different types of eumelanin, which are distinguished from each other by their pattern of polymer bonds. The two types are black eumelanin and brown eumelanin.
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Black eumelanin is the darkest; brown eumelanin is much lighter than black. A small amount of black eumelanin in the absence of other pigments causes grey hair. A small amount of brown eumelanin in the absence of other pigments causes yellow (blond) color hair. Often, natural blond or red hair will darken to a brown color over time.
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Over 95% of melanin content in black and brown hair is eumelanin. Pheomelanin is generally found in elevated concentrations in blond and red hair, representing about one-third of total melanin content. If there is no black eumelanin, the result is strawberry blond. blond hair results from small amounts of brown eumelanin with no black eumelanin.
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The melanin pigments are produced in a specialized group of cells known as melanocytes. There are three basic types of melanin: eumelanin, pheomelanin, and neuromelanin. The most common type is eumelanin, of which there are two types— brown eumelanin and black eumelanin. Pheomelanin is a cysteine-derivative that contains polybenzothiazine portions that are largely responsible for the color of red hair, among other pigmentation.
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As the body ages, it continues to produce black eumelanin but stops producing brown eumelanin, resulting in the grey hair that is common in elderly people.
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UV radiation most commonly comes from the sun, and thus populations from places closer to the equator tend to have darker hair, because eumelanin is generally more photoprotective than pheomelanin. Pheomelanin colors hair orange and red. Eumelanin, which has two subtypes of black or brown, determines the darkness of the hair color; more black eumelanin leads to blacker hair, and more brown eumelanin to browner hair. All human hair has some amount of both pigments.
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A woman with brown hair Brown hair is the second most common human hair color, after black. Brown hair is characterized by higher levels of eumelanin and lower levels of pheomelanin. Of the two types of eumelanin (black and brown), brown-haired people have brown eumelanin; they also usually have medium-thick strands of hair. Brown-haired girls or women are often known as brunettes.
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An agouti hair showing bands of eumelanin and phaeomelanin. Several loci can be grouped as controlling when and where on a dog eumelanin (blacks-browns) or phaeomelanin (reds-yellows) are produced: the Agouti (A), Extension (E) and Black (K) loci. Intercellular signaling pathways tell a melanocyte which type of melanin to produce. Time-dependent pigment switching can lead to the production of a single hair with bands of eumelanin and phaeomelanin.
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The hair color of buried bodies can change. Hair contains a mixture of black-brown-yellow eumelanin and red pheomelanin. Eumelanin is less chemically stable than pheomelanin and breaks down faster when oxidized. The color of hair changes faster under extreme conditions.
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DEFB103 (the K locus) in turn prevents ASIP from inhibiting MC1R, thereby increasing eumelanin synthesis.
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Darkly pigmented skin Dark-skinned humans have high amounts of melanin found in their skin. Melanin is derivative of the amino acid tyrosine. Eumelanin is the dominant form of melanin found in human skin. Eumelanin protects tissues and DNA from the radiation damage of UV light.
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Part of the structural formula of eumelanin. "(COOH)" can be COOH or H, or (more rarely) other substituents. The arrow denotes where the polymer continues. Eumelanin polymers have long been thought to comprise numerous cross-linked 5,6-dihydroxyindole (DHI) and 5,6-dihydroxyindole-2-carboxylic acid (DHICA) polymers.
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Labradors showing the two eumelanin colour phenotypes: Black (BB,Bb) and chocolate (bb). The three recognised colours of Labrador Retrievers result from differences in two genetic loci that affect pigment expression. The first of these affects the colour of the dark pigment, eumelanin, and is referred to as the B (brown) locus. The variation displayed by this locus is observed in many mammals, reflecting a so-called 'dilution', a lightening, of black eumelanin to a brown colour.
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Yellow Labrador with the recessive (ee) and black Labrador with dominant (EE or Ee) phenotype for the expression of eumelanin pigment in the fur. A second gene affects whether these eumelanin pigments will be expressed in the fur or solely in the skin. Called the 'extension' (E) trait, this is directed by the melanocortin 1 receptor (MC1R). This receptor signals the pigment-producing cell in response to melanocortins and results in deposition of eumelanin into the hair.
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Melanin is a derivative of the amino acid tyrosine. Eumelanin is the dominant form of melanin found in human skin. Eumelanin protects tissues and DNA from radiation damage by UV light. Melanin is produced in specialized cells called melanocytes, which are found in the lowest level of the epidermis.
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The sex-linked Orange locus, O/o, determines whether a cat will produce eumelanin. In cats with orange fur, phaeomelanin (red pigment) completely replaces eumelanin (black or brown pigment). This gene is located on the X chromosome. The orange allele is O, and is codominant with non-orange, o.
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When these carotenoids are in short supply, these birds appear white after the next moult. Mutations causing changes in carotenoid-based colour pigments are rare; melanine mutations occur much more frequently. Two types of melanin, eumelanin and phaeomelanin, are present in birds. In the skin and eyes, only eumelanin is present.
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A chocolate Oriental Shorthair kitten. The browning gene B/b/bl codes for TYRP1, an enzyme involved in the metabolic pathway for eumelanin pigment production. Its dominant form, B, will produce black eumelanin. It has two recessive variants, b(chocolate), and bl(cinnamon), with bl being recessive to both B and b.
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Cinnamon and pearl mutations are sex-linked recessive. In Cinnamons, the eumelanin pigment are partially oxidized. Eumelanin granules are stopped at the brown stage of their development to end up in their natural black colour state. They have a specked complexion, with white spots on their secondary feathers and deep brown on their primaries.
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Melanins, which provide color in the eyes, skin, and hair, are found in two types: eumelanin, which produces black to brown pigment, and phaeomelanin, which produces red to yellow pigment. Most horses can produce both types; the brown appearance of a bay horse's coat is caused by alternating bands of eumelanin and phaeomelanin, for which the agouti gene is responsible. Eumelanin predominates in the legs, mane and tail of bay horses. By contrast, horses which lack a functional agouti gene cannot produce such alternating bands, and thus have wholly black coats with no visible phaeomelanin.
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Black hair is the darkest hair color. It has large amounts of eumelanin and is more dense than other hair colors.
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Melanosomes containing eumelanin are eumelanosomes, while those containing phaeomelanin are phaeomelanosomes. Melanocyte-stimulating hormone (MSH) binds to the Melanocortin 1 receptor (MC1R) and commits melanocytes to the production of eumelanin. In the absence of this signal, melanocytes produce phaeomelanin. Another chemical, Agouti signalling peptide (ASP), can attach itself to MC1R and interfere with MSH/MC1R signalling.
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Without melanocortin 1 receptor to signal eumelanin production in melanocytes, this Labrador retriever has a yellow coat. His eyes and skin are normal.
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A tri-color coat is a pattern of some shade of black or brown, few shades of red that is often called tan, and some white. Some have tan markings above the eyes. Eumelanin and phaeomelanin pigmentation occurs on the same dog; "the back is black from eumelanin pigment being made and the belly is tan or red from phaeomelanin pigment being made".
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The white is caused by the recessive piebald gene. It is very rare to get a particolour, and if one is found, it tends to be very expensive."Parti-Color Yorkshire Terriers? ", from the US national breed club Some Yorkshire Terriers are solid golden, they only produce pheomelanin, others are liver or chocolate, a brown colour; they produce brown eumelanin instead of black eumelanin.
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The melanistic mask is caused by the M264V allele (known as EM) at the melanocortin 1 receptor (MC1R) locus, also known as the extension locus. It is completely dominant to the other alleles of the gene, and causes the melanocyte-stimulating hormone to bind to and activate melanocortin 1 receptors (located on melanocytes) in the mask's area, causing those melanocytes to produce eumelanin. Another allele, known as E, is responsible for "normal extension", which allows eumelanin to be produced as usual. e, completely recessive to the other alleles, suppresses all eumelanin production in the coat—the resulting color is sometimes known as recessive red, clear red or Australian red.
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The characteristic pigment of the Callicebus is eumelanin (dark brown or black) found in the iris, skin, and hair (usually on the forehead, crown and tail).
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A critical step in the production of melanins is the catalysis of tyrosine by an enzyme called tyrosinase, producing dopaquinone. Dopaquinone may become eumelanin, or phaeomelanin. Eumelanin, meaning true black, is a dense compound that absorbs most wavelengths of light, and appears black or brown as a result. Phaeomelanin, meaning rufous-black, is characterized by the presence of sulfur-containing cysteine, and it appears reddish to yellowish as a result.
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A woman with dark blonde hair, the basal color appears brown due to higher levels of brownish eumelanin. All natural hair colors are the result of two types of hair pigments. Both of these pigments are melanin types, produced inside the hair follicle and packed into granules found in the fibers. Eumelanin is the dominant pigment in brown hair and black hair, while pheomelanin is dominant in red hair.
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Blond (sometimes blonde for women) hair ranges from nearly white (platinum blond, tow-haired) to a dark golden blond. Strawberry blond, a mixture of blond and red hair, is a much rarer type containing the most pheomelanin. Blond hair can have almost any proportion of pheomelanin and eumelanin, but has only small amounts of both. More pheomelanin creates a more golden or strawberry blond color, and more eumelanin creates an ash or sandy blond color.
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Some humans have very little or no melanin synthesis in their bodies, a condition known as albinism. Because melanin is an aggregate of smaller component molecules, there are many different types of melanin with different proportions and bonding patterns of these component molecules. Both pheomelanin and eumelanin are found in human skin and hair, but eumelanin is the most abundant melanin in humans, as well as the form most likely to be deficient in albinism.
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Pug with black melanistic mask A melanistic mask (also referred to as a mask or masking) is a dog coat pattern that gives the appearance of a mask on the dog's face. The hairs on the muzzle, and sometimes entire face or ears, are colored by eumelanin instead of pheomelanin pigment. Eumelanin is typically black, but may instead be brown, dark gray, or light gray-brown. Pheomelanin ranges in color from pale cream to mahogany.
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Chestnut horses lack the ability to manufacture eumelanin altogether, and so have wholly red coats devoid of true black pigment. Bay silvers retain their reddish body color with black points diluted to silver. While the role of PMEL17 is not fully understood, the silver dapple gene exclusively produces dilution, or hypopigmentation, of eumelanin. The dilution changes black into various shades of platinum, silver and flat grey, though the original black- brown character of the color is usually preserved.
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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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Colour variation within yellow Labradors due to differences in pheomelanin expression. The E locus also determines whether the phenotype due to the third genetic locus affecting coat colour will be evident. This locus is recognised as affecting coat colour through the expression of pheomelanin, the pigment responsible for red and yellow pigmentation. The effects on pheomelanin pigmentation are only seen if there is no eumelanin expressed in the fur, else the dark eumelanin will mask any pheomelanin present.
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In contrast, pocket mice that live on rocks in environments with less sun are more likely to have a selective advantage with darker colored grey or black coats. Genetic Basis 9 day old mice show variation in coat color because of differences in genotype. The genetic difference for varying coat colors is controlled largely by two proteins in pocket mice: eumelanin and pheomelanin. Production of eumelanin gives hair a black or brown color, while pheomelanin gives hair a red color.
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Haas et al., 2005. Melanin is produced inside small membrane-bound packages called melanosomes. Humans with naturally occurring light skin have varied amounts of smaller and scarcely distributed eumelanin and its lighter-coloured relative, pheomelanin.
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The wildtype (natural-coloured or wild occurring) budgerigar's color is called Lightgreen. The feathers of most parrot species, including budgerigars, contain both a black type of melanin named eumelanin along with a basic yellow pigment named psittacofulvin (psittacin for short). Some other parrot species produces a third pigment named advanced-psittacin which enables color & tones ranging from oranges, peaches, pinks to reds. When these feathers are exposed to a white light source, such as sunlight, only the blue part of the spectrum is reflected by the eumelanin granules.
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A man with blond hair and a blond beard Blond or fair hair is a hair color characterized by low levels of the dark pigment eumelanin. The resultant visible hue depends on various factors, but always has some yellowish color. The color can be from the very pale blond (caused by a patchy, scarce distribution of pigment) to reddish "strawberry" blond or golden-brownish ("sandy") blond colors (the latter with more eumelanin). Because hair color tends to darken with age, natural blond hair is significantly less common in adulthood.
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Therefore, Agouti expression causes decreased levels of eumelanin production, which allows increased levels of pheomelanin expression. Variation in the environment can cause proteins to be expressed differently in the genome, producing variation in coat color between two different environments.
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L-tyrosine L-DOPA L-dopaquinone L-leucodopachrome L-dopachrome The first step of the biosynthetic pathway for both eumelanins and pheomelanins is catalysed by tyrosinase. :Tyrosine → DOPA → dopaquinone Dopaquinone can combine with cysteine by two pathways to benzothiazines and pheomelanins :Dopaquinone + cysteine → 5-S-cysteinyldopa → benzothiazine intermediate → pheomelanin :Dopaquinone + cysteine → 2-S-cysteinyldopa → benzothiazine intermediate → pheomelanin Also, dopaquinone can be converted to leucodopachrome and follow two more pathways to the eumelanins :Dopaquinone → leucodopachrome → dopachrome → 5,6-dihydroxyindole-2-carboxylic acid → quinone → eumelanin :Dopaquinone → leucodopachrome → dopachrome → 5,6-dihydroxyindole → quinone → eumelanin Detailed metabolic pathways can be found in the KEGG database (see External links).
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A Labrador Retriever. Note the brown nose, and the yellow in the eyes. In Labradors this color is called "Chocolate," but it is the same as "Liver." In dogs, the Liver color is caused by dilution of the eumelanin (black) pigment by the B locus.
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This is the color of Weimaraners. This color also has alternate names such as Liliac or Silver. When Liver is combined with Merle, the eumelanin (black) pigment is further diluted in random patches. This usually creates a light reddish-gray dog with dark brown patches.
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Activation by α-MSH causes production of the darker eumelanin, while activation by ASIP causes production of the redder phaeomelanin. This means where and while agouti is being expressed, the part of the hair that is growing will come out yellow rather than black.
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Dark skin offers great protection against UVR because of its eumelanin content, the UVR-absorbing capabilities of large melanosomes, and because eumelanin can be mobilized faster and brought to the surface of the skin from the depths of the epidermis. For the same body region, light- and dark-skinned individuals have similar numbers of melanocytes (there is considerable variation between different body regions), but pigment-containing organelles, called melanosomes, are larger and more numerous in dark-skinned individuals. Keratocytes from dark skin cocultured with melanocytes give rise to a melanosome distribution pattern characteristic of dark skin. Melanosomes are not in aggregated state in darkly pigmented skin compared to lightly pigmented skin.
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The main other hypotheses that have been put forward through history to explain the evolution of dark skin coloration relate to increased mortality due to skin cancers, enhanced fitness as a result of protection against sunburns, and increasing benefits due to antibacterial properties of eumelanin. Darkly pigmented, eumelanin-rich skin protects against DNA damage caused by the sunlight. This is associated with lower skin cancer rates among dark-skinned populations. The presence of pheomelanin in light skin increases the oxidative stress in melanocytes, and this combined with the limited ability of pheomelanin to absorb UVR contributes to higher skin cancer rates among light-skinned individuals.
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At minimum, a melanistic mask will appear on the muzzle, and may also be visible on the eartips, entire ears, or entire face. Hairs in those areas will be colored by eumelanin instead of pheomelanin pigment, making it look as though the dog has a mask on its face. Eumelanin is usually black, but may instead be liver (also known as chocolate; dark brown), blue (also known as slate; dark grey), or isabella (also known as lilac; light grey-brown); accordingly, a mask may be any of these colors. Pheomelanin occurs in shades of red ranging from ivory to mahogany, which include cream, gold, and tan.
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A recessive mutation in this E gene truncates the protein, producing a non-functional receptor incapable of directing eumelanin deposition in the fur. Among dogs, this mutation is unique to yellow Labrador Retrievers and Golden Retrievers and is thought to have arisen in the retriever population before these individual breeds became distinct. The exact mutation has also been found to underlie the colouration of white coyotes found around Newfoundland, having apparently passed into that population through interbreeding with a Golden Retriever. As with the B locus, presence of a single copy of the functional receptor gene ('E') will result in the dominant phenotype: presence of eumelanin in the fur.
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"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.Somes, R. G. 1981 International Registry of Poultry Genetic Stocks.
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However, there are only two pigments present, eumelanin and pheomelanin. The overall concentration of these pigments, the ratio between them, variation in the distribution of pigment in the layers of the stroma of the iris and the effects of light scattering all play a part in determining eye color.
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Melanin of different forms combine with xanthophylls to produce colour mixtures and when this combination is imbalanced it produces colour shifts that are termed as schizochroisms (including xanthochromism – overabundance of yellow – and axanthism – lack of yellow – which are commonly bred in cagebirds such as budgerigars). A reduction in eumelanin leads to non- eumelanin schizochroism with an overall fawn plumage while a lack of phaeomelanin results in grey coloured non-phaeomelanin schizochroism. Carotenism refers to abnormal distribution of carotenoid pigments. The term "dilution" is used for situations where the colour is of a lower intensity overall; it is caused by decreased deposition of pigment in the developing feather, and can thus not occur in structural coloration (i.e.
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Inside the melanocytes, tyrosine is converted into L-DOPA and then L-dopaquinone, which in turn is formed into pheomelanin or eumelanin. Different hair color phenotypes arise primarily as a result of varying ratios of these two pigments in the human population, although Europeans show the greatest range in pigmentation overall. In addition, other genetic and environmental factors can affect hair color in humans; for instance, mutations in the melanocortin 1 receptor (MC1R) gene can lead to red or auburn hair, and exposure to ultraviolet radiation can damage hair and alter its pigmentation. Ultraviolet radiation (UV radiation) triggers greater synthesis of several compounds, including pro-opiomelanocortin (POMC), α-MSH, and ACTH, the end result being increased eumelanin production.
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Up to 50% of UVA can penetrate deeply into the dermis in persons with light skin pigmentation with little protective melanin pigment. The characteristic of fair skin, red hair, and freckling is associated with high amount of pheomelanin, little amounts of eumelanin. This phenotype is caused by a loss-of-function mutation in the melanocortin 1 receptor (MC1R) gene. However, variations in the MC1R gene sequence only have considerable influence on pigmentation in populations where red hair and extremely fair skin is prevalent. The gene variation’s primary effect is to promote eumelanin synthesis at the expense of pheomelanin synthesis, although this contributes to very little variation in skin reflectance between different ethnic groups.
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They had flippers instead of legs, and except for early species, had dorsal fins. Although no evidence is specific to Acamptonectes, at least some ichthyosaurs may have been uniformly dark-colored in life, demonstrated by the discovery of high eumelanin contents in the preserved skin of an older ichthyosaur fossil.
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Brown-haired people have medium-thick strands of hair. Brown-haired people are thought to produce more skin-protecting eumelanin and are associated with having a more even skin tone. The range of skin colors associated with brown hair is vast, ranging from the palest of skin tones to a dark olive complexion.
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The weebill is Australia's smallest bird at approximately long and weighing an average of 6 grams (adult bird). Wingspan is approximately . Weebills have inconspicuously coloured plumage ranging from yellowish-grey (front) to olive- brownish-grey (back). The two main feather pigments involved in this variation are yellow (phaeomelanin) and olive-brown (eumelanin).
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Differences in skin color are also attributed to differences in size and distribution of melanosomes in the skin. Melanocytes produce two types of melanin. The most common form of biological melanin is eumelanin, a brown- black polymer of dihydroxyindole carboxylic acids, and their reduced forms. Most are derived from the amino acid tyrosine.
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Methylation on a gene causes the gene to not be expressed because it will cause the promoter to be turned off. In utero, the mother's diet can cause methylation or demethylation. When this area is unmethylated, ectopic expression of agouti occurs, and yellow phenotypes are shown because the phaeomelanin is expressed instead of eumelanin.
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Melanocytes are pigment producing cells, which are controlled by genes. Differences in gene expression cause melanocytes to produce varying levels and types of pigment. Eumelanin is produced when the G protein-coupled receptor called melanocortin-1-receptor (MC1R) is activated. Pheomelanin production is controlled by the agouti-signaling protein, which is an inverse agonist of MC1R.
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Red hair ranges from light strawberry blond shades to titian, copper, and completely red. Red hair has the highest amounts of pheomelanin, around 67%, and usually low levels of eumelanin. At 1–2% of the west Eurasian population, it is the least common hair color in the world. It is most prominently found in the British Isles.
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Spatial-dependent signaling results in parts of the body with different levels of each pigment. MC1R (the E locus) is a receptor on the surface of melanocytes. When active, it causes the melanocyte to synthesize eumelanin; when inactive, the melanocyte produces phaeomelanin instead. ASIP (the A locus) binds to and inactivates MC1R, thereby causing phaeomelanin synthesis.
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Fossilised skin pigmented with dark-coloured eumelanin reveals that both leatherback turtles and mosasaurs had dark backs and light bellies. The ornithischian dinosaur Psittacosaurus similarly appears to have been countershaded, implying that its predators detected their prey by deducing shape from shading. Modelling suggests further that the dinosaur was optimally countershaded for a closed habitat such as a forest.
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Although it is thought to occur in combination with eumelanin in beaks which are buff, tan, or horn-colored, researchers have yet to isolate phaeomelanin from any beak structure.Hill (2010), p. 63. More than a dozen types of carotenoids are responsible for the coloration of most red, orange, and birds never have yellow beaks.Hill (2010), p. 64.
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Some of the fossil's soft tissues remained. The specimen, dating back to 54 Ma, contained eumelanin. This pigment would've given the hatchling a dark shell while it was alive. Modern sea turtle hatchlings also have dark shells; while a hatchling floats on the ocean's surface, its dark coloring enables it to absorb heat from the sun and avoid predatory birds.
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Agouti is not directly secreted in the melanocyte as it works as a paracrine factor on dermal papillae cells to inhibit release of melanocortin. Melanocortin acts on follicular melanocytes to increase production of eumelanin, a melanin pigment responsible for brown and black hair. When agouti is expressed, production of pheomelanin dominates, a melanin pigment that produces yellow or red colored hair.
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A silver tabby British Shorthair. The silver series is caused by the Melanin inhibitor gene I/i. The dominant form causes melanin production to be suppressed, but it affects phaeomelanin (red pigment) much more than eumelanin (black or brown pigment). On tabbies, this turns the background a sparkling silver color while leaving the stripe color intact, making a silver tabby.
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Indian actress Shraddha Kapoor with raven black hair. Black hair is the darkest and most common of all human hair colors globally, due to larger populations with this dominant trait. It is a dominant genetic trait, and it is found in people of all backgrounds and ethnicities. It has large amounts of eumelanin and is less dense than other hair colors.
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In many mammals, variation in the level of ASP switches melanocytes between eumelanin and phaeomelanin production, resulting in coloured patterns. Amelanistic laboratory mice, such as these, have no pigment in their skin, hair, or eyes. Their eyes are reddish. Melanocytes, and the parallel melanophores found in fishes, amphibians, and reptiles, are derived from a strip of tissue in the embryo called the neural crest.
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The front two Rocky Mountain Horses have the silver dapple dilution. The silver dapple trait is caused by a missense mutation (labeled Z) in the PMEL17 gene on horse chromosome 6. It is transmitted by autosomal dominant inheritance (simple dominance). PMEL17 is active from quite early in embryonic development through to the mature cell's melanosome and is involved with the production of the black pigment eumelanin.
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A group of light-skinned people in Europe. Light skin is a human skin color, which has little eumelanin pigmentation and which has been adapted to environments of low UV radiation.light-skinned Princeton University Light skin is most commonly found amongst the native populations of Europe and Asia as measured through skin reflectance. People with light skin pigmentation are often referred to as "white"Oxford Dictionaries.
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Images showing the presence of melanosomes in Gansus and extant (C, D) feathersBarden, H.E. et al. (2011) Morphological and Geochemical Evidence of Eumelanin Preservation in the Feathers of the Early Cretaceous Bird, Gansus yumenensis. PLoS ONE 6(10):e25494. The genus Gansus contains a single species, G. yumenensis, which was about the size of a pigeon and similar in appearance to loons and diving ducks.
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Melanin occurs naturally in the skin and gives skin and hair their color. There are two types of melanin in hair. Eumelanin gives hair brown or black color, while pheomelanin gives hair blonde or red color. Because of the selective absorption of photons of laser light, only hair with color such as black, brown, or reddish-brown hair or dirty blonde can be removed.
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It is characterized by high levels of the reddish pigment pheomelanin (which also accounts for the red color of the lips) and relatively low levels of the dark pigment eumelanin. The term redhead (originally redd hede) has been in use since at least 1510. Cultural reactions have varied from ridicule to admiration; many common stereotypes exist regarding redheads and they are often portrayed as fiery-tempered.
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All of these mutations are found across the range of dogs, and hence are thought to have preceded the divergence of distinct breeds, and all three are found within Labrador Retrievers. Each of the mutations appears to eliminate or significantly reduce enzymatic activity, and the colouration phenotypes (the visible traits) produced by the three mutations are indistinguishable. These represent recessive mutations in the TYRP1 gene, and since mammals have two copies of each gene, one from each parent, an animal with at least one copy of the fully functioning TYRP1 protein (represented as 'B') will display the dominant trait, black pigmentation, while to display brown pigmentation, both copies of this gene must be mutant alleles (collectively represented as 'b'). Thus a dog with the genotypes BB or Bb will express black eumelanin, while brown eumelanin will be seen in dogs with the bb genotype.
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A cat hair showing light and dark bands caused by alternating production of agouti-signaling protein and α-MSH. The agouti gene (ASIP) is responsible for variations in color in many species. Agouti works with extension to regulate the color of melanin which is produced in hairs. The agouti protein causes red to yellow pheomelanin to be produced, while the competing molecule α-MSH signals production of brown to black eumelanin.
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Agouti controls the restriction of true black pigment (eumelanin) in the coat. Horses with the normal agouti gene have the genotype A/A or A/a. Horses without a normal agouti gene have the genotype a/a, and if they are capable of producing black pigment, it is uniformly distributed throughout the coat. A third option, At, restricts black pigment to a black-and-tan pattern called seal brown.
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Additionally, the Agouti locus is the site of mutations in several species that result in black-and-tan pigmentations. In normal horses, ASIP restricts the production of eumelanin to the "points": the legs, mane, tail, ear edges, etc. In 2001, researchers discovered a recessive mutation on ASIP that, when homozygous, left the horse without any ASIP. As a result, horses capable of producing true black pigment had uniformly black coats.
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The full genetic basis of hair color is complex and not fully understood. Regulatory DNA is believed to be closely involved in pigmentation in humans in general, and a 2011 study by Branicki et al. identified 13 DNA variations across 11 different genes that could be used to predict hair color. Two types of pigment give hair its color, black-brown eumelanin and reddish-brown/reddish-yellow pheomelanin, synthesized by melanocytes.
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The fawn coat color is found in many breeds, such as Boxers, Great Danes, and Pugs. Genetically, in most cases the color is due to the recessive ay gene at the Agouti locus. Some breeds, such as Chows and Doberman Pinschers use the term "fawn" to describe a red dog (at the Eumelanin locus) that carries a copy of the dilution gene; in Dobermans this color is more commonly called "Isabella".
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An easy way to tell if a dog is Liver or not is to look at their nose. Eumelanin (black) pigment colors a dog's nose, so a Liver dog will have a Liver colored nose. If the nose is black, the dog is not a liver. A pink nose has nothing to do with liver dilution, and will not help determine if a dog is liver or not.
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Rasagiline, an important monotherapy drug in Parkinson's disease, has melanin binding properties, and melanoma tumor reducing properties. Higher eumelanin levels also can be a disadvantage, however, beyond a higher disposition toward vitamin D deficiency. Dark skin is a complicating factor in the laser removal of port-wine stains. Effective in treating white skin, in general, lasers are less successful in removing port- wine stains in people of Asian or African descent.
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As some of these original people migrated and settled in areas of Asia and Europe, the selective pressure for eumelanin production decreased in climates where radiation from the sun was less intense. This eventually produced the current range of human skin color. Of the two common gene variants known to be associated with pale human skin, Mc1r does not appear to have undergone positive selection, while SLC24A5 has undergone positive selection.
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This analysis of color distribution was based primarily on the distribution of sulphate with the fossil. An author on the previous Archaeopteryx color study argued against the interpretation of copper as an indicator of eumelanin in the full Archaeopteryx specimen but made no mention of the sulphate distribution. A press release and conference abstract by Carney also argue against the 2013 study however, no new evidence has been published.
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Uyghur girl with auburn hair Auburn hair ranges along a spectrum of light to dark red-brown shades. The chemicals which cause auburn hair are eumelanin (brown) and pheomelanin (red), with a higher proportion of red-causing pheomelanin than is found in average brown hair. It is most commonly found in individuals of Northern and Western European descent. It can also be the result of a mutation in the melanocortin 1 receptor gene.
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The second (E) locus determines whether the eumelanin is produced at all. A dog with the recessive e allele will produce only phaeomelanin pigment and will be yellow regardless of its genotype at the B locus. The genes known about previously have had their number increased by the introduction of the K locus, where the dominant "black" allele KB is now known to reside. Black or chocolate Labradors therefore must have the KB allele.
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Melanin is produced in specialized cells called melanocytes, which are found at the lowest level of the epidermis. Melanin is produced inside small membrane-bound packages called melanosomes. People with naturally-occurring dark skin have melanosomes which are clumped, large and full of eumelanin. A four-fold difference in naturally-occurring dark skin gives seven- to eight- fold protection against DNA damage, but even the darkest skin colour cannot protect against all damage to DNA.
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Liver will also dilute a dog's brown eyes to amber/yellow. It is also possible for a dog to be a Liver, and not appear brown. A dog that is recessive red cannot produce eumelanin (black) pigment in their fur. Since Liver is a dilution of black pigment, a recessive red Liver dog will appear to be a shade of Red, Yellow, or Cream depending on the intensity of the dog's phaeomelanin (red) pigment.
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The budgerigar gets its yellow color from a psittacofulvin pigment and its green color from a combination of the same yellow pigment and blue structural color. The blue and white bird in the background lacks the yellow pigment. The dark markings on both birds are due to the black pigment eumelanin. Biological pigments, also known simply as pigments or biochromes, are substances produced by living organisms that have a color resulting from selective color absorption.
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The color of a bird's beak results from concentrations of pigments—primarily melanins and carotenoids—in the epidermal layers, including the rhamphotheca. Eumelanin, which is found in the bare parts of many bird species, is responsible for all shades of gray and black; the denser the deposits of pigment found in the epidermis, the darker the resulting color. Phaeomelanin produces "earth tones" ranging from gold and rufous to various shades of brown.Hill (2010), p. 62.
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Eumelanin is found in hair, areola, and skin, and the hair colors gray, black, blond, and brown. In humans, it is more abundant in people with dark skin. Pheomelanin, a pink to red hue is found in particularly large quantities in red hair, the lips, nipples, glans of the penis, and vagina. Both the amount and type of melanin produced is controlled by a number of genes that operate under incomplete dominance.
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Dun is one of several genes that control the saturation or intensity of pigment in the coat. Dun is unique in that it is simple dominant, affects eumelanin and pheomelanin equally, and does not affect the eyes or skin. Horses with the dominant D allele (D/D or D/d genotype) exhibit hypomelanism of the body coat, while d/d horses have otherwise intense, saturated coat colors. The mane, tail, head, legs, and primitive markings are not diluted.
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A close-up view of brown hair Brown hair is the second most common human hair color, after black hair. It varies from light brown to almost black hair. It is characterized by higher levels of the dark pigment eumelanin and lower levels of the pale pigment pheomelanin. People with brown hair are often referred to as brunette, which in French is the feminine form of brunet, the diminutive of brun (brown, brown-haired or dark-haired).
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These markings are a disqualification for show dogs, but do not have any bearing on the dog's temperament or ability to be a good working dog or pet. Puppies of all colours can potentially occur in the same litter. Colour is determined primarily by three genes. The first gene (the B locus) determines the density of the coat's eumelanin pigment granules, if that pigment is allowed: dense granules result in a black coat, sparse ones give a chocolate coat.
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Zebrafish MC1R mediates the response of fish chromatophores on exposure to dark (top), in comparison to light (bottom), environments. MC1R has a slightly different function in cold-blooded animals such as fish, amphibians, and reptiles. Here, α-MSH activation of MC1R results in the dispersion of eumelanin-filled melanosomes throughout the interior of pigment cells (called melanophores). This gives the skin of the animal a darker hue and often occurs in response to changes in mood or environment.
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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 chickenF. Minvielle, D. Gourichon and J. L. Monvoisin. 2002 Testing homology of loci for two plumage colors, "lavender" and "recessive white", with chicken and Japanese quail hybrids.
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The quantity of melanin pigment in the iris is one factor in determining the phenotypic eye color of a person. Structurally, this huge molecule is only slightly different from its equivalent found in skin and hair. Iris color is due to variable amounts of eumelanin (brown/black melanins) and pheomelanin (red/yellow melanins) produced by melanocytes. More of the former is found in brown-eyed people and of the latter in blue and green-eyed people.
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Melanocytes insert granules of melanin into specialized cellular vesicles called melanosomes. These are then transferred into the keratinocyte cells of the human epidermis. The melanosomes in each recipient cell accumulate atop the cell nucleus, where they protect the nuclear DNA from mutations caused by the ionizing radiation of the sun's ultraviolet rays. In general, people whose ancestors lived for long periods in the regions of the globe near the equator have larger quantities of eumelanin in their skins.
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A hedgehog with albinism due to a genetic mutation Melanin is an organic pigment that produces most of the colour seen in mammals. Depending on how it is created, melanin comes in two colour ranges, eumelanin (producing dark browns and blacks) and pheomelanin (producing light reddish tans and blondes). The dark and light melanins have their influence either alone or in conjunction, making either plain or multi-coloured coats. Sometimes, in a condition called agouti, they make multi-coloured individual hairs.
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On the template of a bay horse, which has eumelanin largely restricted to the points, these points are converted to silver while the phaeomelanic body is mostly unaffected. An undesirable effect associated with the gene is eye problems, notably multiple congenital ocular anomalies (MCOA). MCOA has multiple clinical signs including a bulbous bulging of the eye, cornea globosa, severe iridal hypoplasia, uveal cysts, cataracts, and in a few cases, retinal detachment. These conditions can be detected via ultrasound examination of the eye.
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In many species, successive pulses of ASIP block contact between α-MSH and MC1R, resulting in alternating production of eumelanin and pheomelanin; hairs are banded light and dark as a result. In other species, ASIP is regulated such that it only occurs in certain parts of the body. The light undersides of most mammals are due to the carefully controlled action of ASIP. In mice, two mutations on Agouti are responsible for yellow coats and marked obesity, with other health defects.
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The gene for "red" color is designated as "e". This is because the presence or absence of red color in horses is determined by the equine melanocortin 1 receptor (MC1R), a protein positioned on chromosome 3 (ECA3) at the Extension locus. The wild type version of the gene encoding MC1R is the E allele (colloquially, though imprecisely, called the "Extension gene"), and is part of the genetic pathway that allows melanocytes to produce eumelanin, or black pigment.Online Mendelian Inheritance in Man, OMIM (TM).
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Agouti-signaling protein is a protein that in humans is encoded by the ASIP gene. It is responsible for the distribution of melanin pigment in mammals. Agouti interacts with the melanocortin 1 receptor to determine whether the melanocyte (pigment cell) produces phaeomelanin (a red to yellow pigment), or eumelanin (a brown to black pigment). This interaction is responsible for making distinct light and dark bands in the hairs of animals such as the agouti, which the gene is named after.
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The effects of the gene are more striking in the mane and tail. Horses with chestnut or chestnut-family coats - such as palomino, red roan, or red dun - are therefore unaffected by the gene and may silently carry it and pass it on to their offspring. On the template of a black horse, which has a coat rich in eumelanin, the effect is that of complete conversion to varying shades of silver. Often the body remains quite dark while the mane and tail are strongly diluted.
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Genes affecting coat color generally do so by changing the process of producing melanin. Melanin is the pigment that colors the hairs and skin of mammals. There are two chemically distinct types of melanin: pheomelanin, which is a red to yellow color, and eumelanin, which is brown to black. Melanin is not a protein and therefore there is no gene that changes its structure directly, but there are many proteins involved in the production of melanin or the formation of melanocytes during embryonic development.
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A close-up view of red hair Roman fresco of a woman with red hair wearing a garland of olives, from Herculaneum, made sometime before the city's destruction in 79 AD by Mount Vesuvius (which also destroyed Pompeii). The pigment pheomelanin gives red hair its distinctive color. Red hair has far more of the pigment pheomelanin than it has of the dark pigment eumelanin. The genetics of red hair appear to be associated with the melanocortin-1 receptor (MC1R), which is found on chromosome 16.
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The Lutino sex-linked recessive mutation is a perfect example of a type of cockatiel that are the hardest to sex visually. Lutinos lack eumelanin pigment (enabling black, brown, grey colours and tones) and are consequently yellow to yellowish-white with orange cheek-patches. Adult female Lutinos as well as immature Lutinos of both genders display yellow bars, dots and/or stripes on the underside of their tail feathers. Mature males, however, can be sexed visually by their always displaying solid white coloured undersides of tail feathers.
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When the region is methylated, agouti is expressed normally, and grey and brown phenotypes (eumelanin) occur. The epigenetic state of the IAP element is determined by the level of methylation, as individuals show a wide range of phenotypes based on their degree of DNA methylation. Increased methylation is correlated with increased expression of the normal agouti gene. Low levels of methylation can induce gene imprinting which results in offspring displaying consistent phenotypes to their parents, as ectopic expression of agouti is inherited through non-genomic mechanisms.
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Labrador Retrievers are a popular dog breed in many countries. There are three recognised colours, black, chocolate, and yellow,Carol Coode, Labrador Retrievers Today, Howell Book House: New York, 1993. that result from the interplay among genes that direct production and expression of two pigments, eumelanin (brown or black pigment) and pheomelanin (yellow to red pigment), in the fur and skin of the dog. The recognized colours are due to two genes, while a third gene affects the range of colouration observed within the yellow Labrador.
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In some bird species, the colour is completely caused by eumelanin, however, both types of melanin are found in most species. In birds, albinism has been defined as "a total lack of both melanins in feathers, eyes and skin as a result of an inherited absence of tyrosinase", however, this ignores the effects of other pigments and structural colours. An albino bird has a white beak, white plumage, non-coloured skin, white talons and pink or red eyes. Albinism is only seen in about 1 of every 1,800 birds.
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Journal of Heredity 31:291-292. described a different autosomal recessive mutation known as "pink eye" (pk) that severely reduce pigmentation in the eyes, but only dilutes the pigment in the plumage, so this mutation does not produce a solid white color. The ultra-structure of "pink eye" melanocytes from both the eyes and feathers of embryo chicks and adults has been extensively defined.Brumbaugh, J.A. 1968 Ultrastructural differences between forming eumelanin and pheomelanin as revealed by the pink-eye mutation in the fowl. Develop. Biol. 18:375-390.
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Eighty percent of redheads have an MC1R gene variant. Red hair is associated with fair skin color because low concentrations of eumelanin throughout the body of those with red hair caused by a MC1R mutation can cause both. The lower melanin concentration in skin confers the advantage that a sufficient concentration of important Vitamin D can be produced under low light conditions. However, when UV-radiation is strong (as in regions close to the equator) the lower concentration of melanin leads to several medical disadvantages, such as a higher risk of skin cancer.
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MC1R is one of the key proteins involved in regulating mammalian skin and hair color. It is located on the plasma membrane of specialized cells known as melanocytes, which produce the pigment melanin through the process of melanogenesis. It works by controlling the type of melanin being produced, and its activation causes the melanocyte to switch from generating the yellow or red phaeomelanin by default to the brown or black eumelanin in replacement. MC1R has also been reported to be involved in cancer (independent of skin coloration), developmental processes, and susceptibility to infections and pain.
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"[Y]ellow mice are often characterized...by variable degrees of sootiness. In some animals the sootiness is confined to a mid- dorsal streak, in others this streak is wider, covering the entire back and sometimes the flanks, so that only the belly is phenotypically "yellow." This situation is due to the admixture of hairs possessing significant amounts of eumelanin to the yellow fur." A statistical analysis of 1369 offspring of five Franches-Montagnes stallions indicated that darker shades of chestnut and bay might follow a recessive mode of inheritance.
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Chocolate and lilac Himalayans usually have bigger markings than blacks and blues, and are more likely to develop disqualifying markings, known as "smut". Himalayans may develop smut after just ten minutes of contact to cold objects. Baby Himalayans are especially sensitive to temperature. Most babies in the warmth of the nest will look the same as albino babies (because Himalayans can only produce eumelanin under a certain temperature and they cannot produce pheomelanin at all.) Himalayans will always have red eyes, and any Himalayan marked rabbits without red eyes are usually misidentified sable points.
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A sun tanned arm showing browner skin where it has been exposed Melanin is a natural pigment produced by cells called melanocytes in a process called melanogenesis. Melanocytes produce two types of melanin: pheomelanin (red) and eumelanin (very dark brown). Melanin protects the body by absorbing ultraviolet radiation. Excessive UV radiation causes sunburn along with other direct and indirect DNA damage to the skin, and the body naturally combats and seeks to repair the damage and protect the skin by creating and releasing further melanin into the skin's cells.
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The melanocortin 1 receptor (MC1R) is a transmembrane and G-protein coupled receptor expressed in melanocytes. MC1R is an important target for the regulation of melanogenesis. Agonism of MC1R increases the ratio of eumelanin to pheomelanin and increases the generation of melanin overall. The MC1R and cAMP signaling pathway starts with the activation of MC1R, which causes activation of adenylyl cyclase (AC), which produces cyclic adenosine monophosphate (cAMP), which activates protein kinase A (PKA), which activates by protein phosphorylation cAMP response element- binding protein (CREB), which upregulates MITF, of which CREB is a transcription factor.
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The MC1R protein lies within the cell membrane, and is signalled by melanocyte-stimulating hormone (MSH) released by the pituitary gland. When activated by one of the variants of MSH, typically α-MSH, MC1R initiates a complex signaling cascade that leads to the production of the brown or black pigment eumelanin. In contrast, the receptor can also be antagonized by agouti signalling peptide (ASIP), which reverts the cell back to producing the yellow or red phaeomelanin. The pulsatile nature of ASIP signalling through MC1R produces the characteristic yellow and black agouti banding pattern observed on most mammalian hair.
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Although it is true that eumelanin has antibacterial properties, its importance is secondary to 'physical adsorption' (physisorption) to protect against UVR-induced damage. This hypothesis is not consistent with the evidence that most of the hominid evolution took place in savanna environments and not in tropical rainforests. Humans living in hot and sunny environments have darker skin than humans who live in wet and cloudy environments. The antimicrobial hypothesis also does not explain why some populations (like the Inuit or Tibetans) who live far from the tropics and are exposed to high UVR have darker skin pigmentation than their surrounding populations.
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Pheomelanins are particularly concentrated in the lips, nipples, glans of the penis, and vagina. When a small amount of brown eumelanin in hair, which would otherwise cause blond hair, is mixed with red pheomelanin, the result is orange hair, which is typically called "red" or "ginger" hair. Pheomelanin is also present in the skin, and redheads consequently often have a more pinkish hue to their skin as well. In chemical terms, pheomelanins differ from eumelanins in that the oligomer structure incorporates benzothiazine and benzothiazole units that are produced, instead of DHI and DHICA, when the amino acid L-cysteine is present.
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Of the hundreds of surviving skins, only one appears to be aberrant in coloran adult female from the collection of Walter Rothschild, Natural History Museum at Tring. It is a washed brown on the upper parts, wing covert, secondary feathers, and tail (where it would otherwise have been gray), and white on the primary feathers and underparts. The normally black spots are brown, and it is pale gray on the head, lower back, and upper-tail covert feathers, yet the iridescence is unaffected. The brown mutation is a result of a reduction in eumelanin, due to incomplete synthesis (oxidation) of this pigment.
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Typically, between 1000 and 2000 melanocytes are found per square millimeter of skin or approximately 5% to 10% of the cells in the basal layer of epidermis. Although their size can vary, melanocytes are typically 7 μm in length. The difference in skin color between lightly and darkly pigmented individuals is due not to the number (quantity) of melanocytes in their skin, but to the melanocytes' level of activity (quantity and relative amounts of eumelanin and pheomelanin). This process is under hormonal control, including the MSH and ACTH peptides that are produced from the precursor proopiomelanocortin.
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In some birds – many true owls (Strigidae), some nightjars (Caprimulgidae) and a few cuckoos (Cuculus and relatives) being widely known examples – there is colour polymorphism. This means that two or more colour variants are numerous within their populations during all or at least most seasons and plumages; in the above-mentioned examples a brown (phaeomelanin) and grey (eumelanin) morph exist, termed "hepatic form" particularly in the cuckoos. Other cases of natural polymorphism are of various kinds; many are melanic/nonmelanic (some paradise-flycatchers, Terpsiphone, for example), but more unusual types of polymorphism exist – the face colour of the Gouldian finch (Erythrura gouldiae) or the courtship types of male ruffs (Philomachus pugnax).
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Uyghur girl in Kashgar, China's Xinjiang region, with auburn hair Auburn hair is a variety of red hair, most commonly described as reddish-brown in color or dark ginger. Auburn hair ranges in shades from medium to dark. It can be found with a wide array of skin tones and eye colors. The chemical pigments that cause the coloration of auburn hair are frequently pheomelanin with high levels of eumelanin; however, the auburn hair is due to a mutated melanocortin 1 receptor gene in Northwestern European people and by a mutated TYRP1 gene in the Melanesians and Austronesians, both genes that reduce the melanin production of the hair cells.
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This allele is recessive to A and dominant to a, such that horses with the genotype A/At appear bay, while At/At and At/a horses are seal brown in the presence of a dominant Extension allele E. The Agouti locus is occupied by the Agouti signalling peptide (ASIP) gene, which encodes the eponymous protein (ASIP). Agouti signalling peptide is a paracrine signaling molecule that competes with alpha-melanocyte stimulating hormone (α-MSH) for melanocortin 1 receptor proteins (MC1R). MC1R relies on α-MSH to halt production of red- yellow pheomelanin, and initiate production of black-brown eumelanin in its place. Johns Hopkins University, Baltimore, MD. Accessed 9/4/2008.
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Camouflage is a soft-tissue feature that is rarely preserved in the fossil record, but rare fossilised skin samples from the Cretaceous period show that some marine reptiles were countershaded. The skins, pigmented with dark-coloured eumelanin, reveal that both leatherback turtles and mosasaurs had dark backs and light bellies. There is fossil evidence of camouflaged insects going back over 100 million years, for example lacewings larvae that stick debris all over their bodies much as their modern descendants do, hiding them from their prey. Dinosaurs appear to have been camouflaged, as a 120 million year old fossil of a Psittacosaurus has been preserved with countershading.
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The primary factor contributing to the evolution of dark skin pigmentation was the breakdown of folate in reaction to ultraviolet radiation; the relationship between folate breakdown induced by ultraviolet radiation and reduced fitness as a failure of normal embryogenesis and spermatogenesis led to the selection of dark skin pigmentation. By the time modern Homo sapiens evolved, all humans were dark-skinned. Humans with dark skin pigmentation have skin naturally rich in melanin (especially eumelanin), and have more melanosomes which provide superior protection against the deleterious effects of ultraviolet radiation. This helps the body to retain its folate reserves and protects against damage to DNA.
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This is because the feather barbles of the colored spot contain melanin pigments - mainly eumelanin, which was equivalent to 83% of all melanins, but also pheomelanin at a concentration approximately equal to that of carotenoids, which seems to be a rare trait for carotenoid-based ornamental plumage. On the other hand, the feathers of the yellow stripes of the males are devoid of carotenoids —except occasionally when they appear tinged with a pink coloration derived from small amounts of said pigments— and present high concentrations of pheomelanin —82% of all melanins. Melanin concentrations in the yellow band are even higher than in the red spot.
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Fossil Loligosepia aalensis from the lower Jurassic; the ink sac is still full of black eumelanin pigment Squid distract attacking predators by ejecting a cloud of ink, giving themselves an opportunity to escape. The ink gland and its associated ink sac empties into the rectum close to the anus, allowing the squid to rapidly discharge black ink into the mantle cavity and surrounding water. The ink is a suspension of melanin particles and quickly disperses to form a dark cloud that obscures the escape manoeuvres of the squid. Predatory fish may also be deterred by the alkaloid nature of the discharge which may interfere with their chemoreceptors.
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Melanocytes, the cells that produce pigment in skin and hair, use the MC1R to recognize and respond to MSH from the anterior pituitary gland. Melanocyte- stimulating hormone normally stimulates melanocytes to make black eumelanin, but if the melanocytes have a mutated receptor, they will make reddish pheomelanin instead. MC1R also occurs in the brain, where it is one of a large set of POMC-related receptors that are apparently involved not only in responding to MSH, but also in responses to endorphins and possibly other POMC-derived hormones. Though the details are not clearly understood, it appears that there is some crosstalk between the POMC hormones; this may explain the link between red hair and pain tolerance.
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Evolutionary developmental biology has assembled evidence from embryology and genetics to show how evolution has acted at all scales from the whole organism down to individual genes, proteins and genetic switches. In the case of countershaded mammals with dark (often brownish) upper parts and lighter (often buff or whitish) under parts, such as in the house mouse, it is the Agouti gene which creates the difference in shading. Agouti encodes for a protein, the Agouti signalling peptide (ASP), which specifically inhibits the action of the Melanocortin 1 receptor (MC1R). In the absence of the Agouti protein, alpha-melanocyte-stimulating hormone stimulates the cells bearing MC1R, melanocytes, to produce dark eumelanin, colouring the skin and fur dark brown or black.
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This is caused by the insertion of a single intracisternal A particle (IAP) retrotransposon upstream to the start site of agouti transcription. In the proximal end of the gene, an unknown promoter then causes agouti to be constitutionally activated, and individuals to present with phenotypes consistent with the lethal yellow mutation. Although the mechanism for the activation of the promoter controlling the viable yellow mutation is unknown, the strength of coat color has been correlated with the degree of gene methylation, which is determined by maternal diet and environmental exposure. As agouti itself inhibits melanocortin receptors responsible for eumelanin production, the yellow phenotype is exacerbated in both lethal yellow and viable yellow mutations as agouti gene expression is increased.
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The Alagoas curassow was first mentioned by German naturalist Georg Marcgrave in his work Historia Naturalis Brasiliae which was published in 1648. Because of the lack of information and specimens, it was considered conspecific with the common razor-billed curassow, until its rediscovery in 1951 in the Alagoas lowland forests, Brazil. Following the review of Pereira & Baker (2004), they are today believed to be a fairly basal lineage of its genus, related to the crestless curassow, the other Mitu species with brown eumelanin in the tail tip. Its lineage has been distinct since the Miocene-Pliocene boundary (approximately 5 million years ago), when it became isolated in refugia in the Atlantic Forest (Pereira & Baker 2004).
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Tortoiseshell and calico coats result from an interaction between genetic and developmental factors. The primary gene for coat color (B) for the colors brown, chocolate, cinnamon, etc., can be masked by the co-dominant gene for the orange color (O) which is on the X Chromosome and has two alleles, the orange (XO) and not-orange (Xo), that produce orange phaeomelanin and black eumelanin pigments, respectively. (NOTE: Typically, the X for the chromosome is assumed from context and the alleles are referred to by just the uppercase O for the orange, or lower case o for the not-orange.) The tortoiseshell and calico cats are indicated: Oo to indicate they are heterozygous on the O gene.
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" Champagne differs from Dun in that it affects the color of the coat, skin, and eyes, and in that the unaffected condition is the wildtype. Horses with the dominant CH allele (CH/CH or CH/ch genotype) exhibit hypomelanism of the body coat, such that phaeomelanin is diluted to gold and eumelanin is diluted to tan. Affected horses are born with blue eyes which darken to amber, green, or light brown, and bright pink skin which acquires darker freckling with maturity.Cook et al. 2008. "...champagne foals are born with blue eyes, which change color to amber, green, or light brown and pink “pumpkin skin which acquires a darker mottled complexion around the eyes, muzzle, and genitalia as the animal matures.
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Early humans evolved to have dark skin color around 1.2 million years ago, as an adaptation to a loss of body hair that increased the effects of UV radiation. Before the development of hairlessness, early humans had reasonably light skin underneath their fur, similar to that found in other primates. The most recent scientific evidence indicates that anatomically modern humans evolved in Africa between 200,000 and 100,000 years, and then populated the rest of the world through one migration between 80,000 and 50,000 years ago, in some areas interbreeding with certain archaic human species (Neanderthals, Denisovans, and possibly others). It seems likely that the first modern humans had relatively large numbers of eumelanin-producing melanocytes, producing darker skin similar to the indigenous people of Africa today.
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The lethal yellow (Ay) mutation is due to an upstream deletion at the start site of agouti transcription. This deletion causes the genomic sequence of agouti to be lost, except the promoter and the first non-encoding exon of Raly, a ubiquitously expressed gene in mammals. The coding exons of agouti are placed under the control of the Raly promoter, initiating ubiquitous expression of agouti, increasing production of pheomelanin over eumelanin and resulting in the development of a yellow phenotype.Proposed mechanism for the relationship between ectopic agouti expression and the development of yellow obese syndrome The viable yellow (Avy) mutation is due to a change in the mRNA length of agouti, as the expressed gene becomes longer than the normal gene length of agouti.
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In modern humans, skin and hair colour is regulated by the melanocyte-stimulating hormone—which increases the proportion of eumelanin (black pigment) to phaeomelanin (red pigment)—which is encoded by the MC1R gene. There are 5 known variants in modern humans of the gene which cause loss-of-function and are associated with light skin and hair colour, and another unknown variant in Neanderthals (the R307G variant) which could be associated with pale skin and red hair. The R307G variant was identified in a Neanderthal from Monti Lessini, Italy, and possibly Cueva del Sidrón, Spain. However, as in modern humans, red was probably not a very common hair colour because the variant is not present in many other sequenced Neanderthals.
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Mutations in this protein have been shown to be involved in pale or red colour phenotypes in a range of species, including humans, horses, pigs, cattle, mice, fur seals, mammoths and the Kermode bear, as well as colouration in whiptail lizards. In most dogs, activity of MC1R is modulated by two signaling molecules, a repressor that is a product of the Agouti gene (A locus), and an activator, β-Defensin 103 (CBD103), recently named the K locus. In Labradors a highly-active mutated version of the K gene, (KB) is invariant, producing uniform eumelanin distribution independent of the Agouti genotype and leaving differences in MC1R to mediate the sole variability of this signaling pathway.Ruvinsky, A., Sampson, J. The Genetics of the Dog, 2001, Wallingford, Oxfordshire, UK, ebook.
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Woman with red hair Actor Rupert Grint with red hair Ogëdei Khan, son of Genghis Khan Red hair (or ginger hair) occurs naturally in one to two percent of the human population, appearing with greater frequency (two to six percent) among people of Northern or Northwestern European ancestry and lesser frequency in other populations. It is most common in individuals homozygous for a recessive allele on chromosome 16 that produces an altered version of the MC1R protein. Red hair varies in hue from a deep burgundy or bright copper, or auburn, to burnt orange or red-orange to strawberry blond. Characterized by high levels of the reddish pigment pheomelanin and relatively low levels of the dark pigment eumelanin, it is associated with fair skin color, lighter eye color, freckles, and sensitivity to ultraviolet light.
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There are several different types of melanins considering that they are an aggregate of smaller component molecules, such as nitrogen containing melanins. There are two classes of pigments: black and brown insoluble eumelanins, which are derived from aerobic oxidation of tyrosine in the presence of tyrosinase, and the alkali-soluble phaeomelanins which range from a yellow to red brown color, arising from the deviation of the eumelanin pathway through the intervention of cysteine and/or glutathione. Eumelanins are usually found in the skin and eyes. Several different melanins include melanoprotein (dark brown melanin that is stored in high concentrations in the ink sac of the cuttlefish Sepia Officianalis), echinoidea (found in sand dollars, and the hearts of sea urchins), holothuroidea (found in sea cucumbers), and ophiuroidea (found in brittle and snake stars).
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Initial genetic research excluded a role for the melanocortin 1 receptor and the Agouti locus as being the cause of the black dilution trait in dogs.J.A. Kerns, M. Oliver, G. Lust and G. S. Barsh, "Exclusion of Melanocortin-1 Receptor (Mc1r) and Agouti as Candidates for Dominant Black in Dogs", Journal of Heredity, 94: 75-79 (2003) Instead, TYRP1 (tyrosinase related protein 1) was found to be responsible. This enzyme is localised to melanosomes, the cellular organelles that produce and store pigments, and serves to catalyze oxidation of eumelanin precursors. In dogs, three mutations in the TYRP1 gene have been identified, one resulting in a truncation of the protein, the other two leading to an amino acid deletion or a single amino acid substitution in the sequence of the protein.
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As birds become flightless, their feathers soon lose the barbule hooks that keep them in shape, becoming more hair-like; when flight performance is of no significance anymore, this can improve the insulating properties of the plumage. Nothing is known about the plumage color of Eremopezus; it was presumably not very gaudily colored as it had to avoid apex predators, but little else can be inferred. Perhaps most likely it had white, black or grey feathers with at least some eumelanin but little carotenoids and phaeomelanins, as usual among the "higher waterbirds" in general, and specifically those that inhabit similar habitat. If it was a terrestrial animal, it might have been fairly short-necked; if it inhabited wetlands, its neck was probably not short and quite possibly rather long.
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Johns Hopkins University, Baltimore, MD. MIM Number: 155555: 15 Feb. 2008: When the "E" allele is not present, no eumelanin is produced, but the "e" allele still allows melanin to be produced in the form of pheomelanin, or red pigment, creating a chestnut or red-based coat color. In general, alleles that create fully functional MC1R proteins are inherited dominantly and result in a black-based coat color ("E"), while mutated alleles that create "dysfunctional" MC1R are recessive and result in a lighter coat color ("e"). Red hair color in horses ("e") is created by a missense mutation in the code for MC1R, which results in a protein that cannot bind to the Melanocyte- stimulating hormone (MSH), which is released by the pituitary gland, and stimulates the production and release of melanin in skin and hair.
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In mice, the agouti gene encodes a paracrine signalling molecule that causes hair follicle melanocytes to synthesize the yellow pigment pheomelanin instead of the black or brown pigment eumelanin. Pleiotropic effects of constitutive expression of the mouse gene include adult-onset obesity, increased tumor susceptibility, and premature infertility. This gene is highly similar to the mouse gene and encodes a secreted protein that may (1) affect the quality of hair pigmentation, (2) act as an inverse agonist of alpha-melanocyte-stimulating hormone, (3) play a role in neuroendocrine aspects of melanocortin action, and (4) have a functional role in regulating lipid metabolism in adipocytes. In mice, the wild type agouti allele (A) presents a grey phenotype, however, many allele variants have been identified through genetic analyses, which result in a wide range of phenotypes distinct from the typical grey coat.
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It is suggested that the early genus Homo (humans in the broader sense) started to evolved in East Africa around 3 million years ago. The dramatic phenotypic change from the ape-like Australopithecus to early Homo is hypothesized to have involved the extreme loss of body hair – except for areas most exposed to UV radiation, such as the head – to allow for more efficient thermoregulation in the early hunter-gatherers. The skin that would have been exposed upon general body hair loss in these early proto-humans would have most likely been non-pigmented, reflecting the pale skin underlying the hair of our chimpanzee relatives. A positive advantage would have been conferred to early hominids inhabiting the African continent that were capable of producing darker skin – those who first expressed the eumelanin-producing MC1R allele – which protected them from harmful epithelium-damaging ultraviolet rays.
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Thus these differences are visible only in yellow Labradors, which as a result range in colour from light cream to copper-red. It had long been thought that the genetic locus for this trait was the same seen regulating pheomelanin in other mammals, subsequently identified as tyrosinase. This enzyme makes both eumelanin and pheomelanin, and when subject to a knockout mutation results in albinism. A less extreme mutation of the same tyrosinase gene, the so-called Chinchilla trait, produces a dilution that selectively affects pheomelanin alone, similar to the phenotype observed in yellow Labradors. Thus, as with Chinchilla-related pheomelanin dilution in other species, this trait in yellow Labradors has been represented by the letter C. However, genetic analysis of the inheritance of coat colour in yellow Labradors has shown that the locus responsible is entirely distinct from the Chinchilla trait of the tyrosinase gene, and likewise is distinct from SLC45A2,Sheila M. Schmutz and Tom G. Berryere, The Genetics of Cream Coat Color in Dogs, Journal of Heredity, 98: 544-548 (2007) the so-called cream gene responsible for the dilution of pheomelanin in buckskin, palomino and cremello horses and also for the absence of pheomelanin in the white tiger,Xiao Xu, et al.
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