Melanin is a polymer of either or both of two monomer molecules: indolequinone, and dihydroxyindole carboxylic acid. Melanin exists in the plant, animal and protista kingdoms, where, among other functions, it serves as a pigment. The presence of melanin in the archaea and bacteria kingdoms is an issue of ongoing scholarly disagreement. A polymer is a generic term used to describe a substantially long molecule. ... In chemistry, a monomer (from Greek mono one and meros part) is a small molecule that may become chemically bonded to other monomers to form a polymer. ... In science, a molecule is the smallest particle of a pure chemical substance that still retains its chemical composition and properties. ... Divisions Green algae Land plants (embryophytes) Non-vascular embryophytes Hepatophyta - liverworts Anthocerophyta - hornworts Bryophyta - mosses Vascular plants (tracheophytes) Seedless vascular plants Lycopodiophyta - clubmosses Equisetophyta - horsetails Pteridophyta - true ferns Psilotophyta - whisk ferns Ophioglossophyta - adderstongues Seed plants (spermatophytes) †Pteridospermatophyta - seed ferns Pinophyta - conifers Cycadophyta - cycads Ginkgophyta - ginkgo Gnetophyta - gnetae Magnoliophyta - flowering plants... Phyla Porifera (sponges) Ctenophora (comb jellies) Cnidaria Placozoa Bilateria  Acoelomorpha  Orthonectida  Rhombozoa  Myxozoa  Superphylum Deuterostomia     Chordata (vertebrates, etc. ... Typical phyla Rhodophyta (red algae) Chromista Heterokontophyta (heterokonts) Haptophyta Cryptophyta (cryptomonads) Alveolates Pyrrhophyta (dinoflagellates) Apicomplexa Ciliophora (ciliates) Excavates Euglenozoa Percolozoa Metamonada Rhizaria Radiolaria Foraminifera Cercozoa Amoebozoa Choanozoa Many others; classification varies The Kingdom Protista or Protoctista is one of the commonly recognized biological kingdoms, including all the eukaryotes except for... In biology, pigment is any material resulting in color in plant or animal cells which is the result of selective absorption. ...

Melanin in humans

In humans melanin is found in skin, hair, the coat of the retina, the medulla and zona reticularis of the adrenal gland, the inner ear, and the substantia nigra (in Latin, literally "black substance) of the brain. Melanin is produced by melanocytes, which in the skin are found in the stratum basale of the epidermis. Although human beings generally possess a similar concentration of melanocytes in their skin, the melanocytes in some individuals and races more frequently express the melanin-producing genes, thereby conferring a greater concentration of skin melanin. Some individual animals and humans have no or very little melanin in their bodies, which is a condition known as albinism. Model of the layers of human skin In zootomy and dermatology, skin is an organ of the integumentary system; which is composed of a layer of tissues that protect underlying muscles and organs. ... Long braided hair Hair is the filamentous outgrowth of the epidermis found in mammals. ... Human eye cross-sectional view. ... In mammals, the adrenal glands are the triangle-shaped endocrine glands that sit atop the kidneys. ... For an alternative meaning, see ear (botany). ... The substantia nigra (Latin for black substance) is a portion of the midbrain thought to be involved in certain aspects of movement and attention. ... Latin is the language originally spoken in the region around Rome called Latium. ... Picture of a human brain generated from MRI data Sagittal slice from a fMRI scan of a human brain. ... Melanocytes are cells located in the bottom layer of the skins epidermis. ... Model of the layers of human skin In zootomy and dermatology, skin is an organ of the integumentary system; which is composed of a layer of tissues that protect underlying muscles and organs. ... Stratum germinativum or stratum basale is the layer of keratinocytes that lies at the base of the epidermis immediately above the dermis. ... Epidermis is the outermost layer of the skin. ... Albinism is a genetic condition resulting in a lack of pigmentation in the eyes, skin and hair. ...

Because melanin is an aggregate of smaller component molecules, there are a number of different types of melanin with differing 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. Albinism is a genetic condition resulting in a lack of pigmentation in the eyes, skin and hair. ...

Eumelanin polymers have long been thought to comprise numerous cross-linked dihydroxyindole polymers; recent research into the electrical properties of eumelanin, however, has indicated that it may consist of more basic oligomers adhering to one another by some other mechanism. Thus, the precise nature of eumelanin's molecular structure is once again the object of study. Eumelanin is found in hair and skin and colors hair from brown to black. In humans, it is more abundant in peoples with dark skin. A polymer is a generic term used to describe a substantially long molecule. ... In chemistry, an oligomer consists of a finite number of monomer units (oligo is Greek for a few), in contrast to a polymer which, at least in principle, consists of an infinite number of monomers. ...

Pheomelanin is also found in hair and skin and is more abundant in fair-skinned humans. Pheomelanin imparts a yellow to reddish hue and, thus, is found in particularly large quantities in red hair.

Neuromelanin is a byproduct of dopamine metabolism, and is found in the substantia nigra of the human brain and the inner ear. Its role is uncertain, but neuromelanin, as its name suggests, is a known neurotransmitter.

Melanin deficiency in genetic disorders and disease states

Melanin deficiency definitively has been connected for some time with various genetic abnormalities and disease states.

While people with albinism have normal amounts of neuromelanin in their brains, there has been a fairly well known, but little-understood, connection between albinism and deafness in certain mammals for more than a century and-a-half. In fact, Charles Darwin observed such a connection in albino cats in his 1859 treatise On the Origin of Species. Neuromelanin is not present in the brains of all mammals, but it has been detected in primates and some carnivores, like cats and dogs. Interestingly, similar patterns of albinism and deafness have been found in other mammals, including dogs, rodents and humans. Further, persons with Parkinson's disease, a disorder which affects neuromotor functioning, have been shown to have melanin deficients in the substantia nigra. Charles Darwin, about the same time as the publication of The Origin of Species. ... The 1859 edition of On the Origin of Species First published in 1859, The Origin of Species (full title On the Origin of Species by Means of Natural Selection, or the Preservation of Favoured Races in the Struggle for Life) by British naturalist Charles Darwin is one of the pivotal... Orders Subclass Monotremata Monotremata Subclass Marsupialia Didelphimorphia Paucituberculata Microbiotheria Dasyuromorphia Peramelemorphia Notoryctemorphia Diprotodontia Subclass Placentalia Xenarthra Dermoptera Desmostylia Scandentia Primates Rodentia Lagomorpha Insectivora Chiroptera Pholidota Carnivora Perissodactyla Artiodactyla Cetacea Afrosoricida Macroscelidea Tubulidentata Hyracoidea Proboscidea Sirenia The mammals are the class of vertebrate animals primarily characterized by the presence of mammary... For the ecclesiastical use of this term, see primate (religion) Families 13, See classification A primate is any member of the biological order Primates, the group that contains all lemurs, monkeys, and apes, including humans. ... This article deals with meat-eating animals. ... This article is about Cats, the musical. ... For other members of the dog family, see Canidae. ...

Melanin and human adaptation

Melanocytes insert granules of melanin called melanosomes into the other skin cells of the human epidermis. The melanosomes in each recipient cell accumulate atop the cellular nucleus, where they protect the nuclear DNA from mutations caused by the sun's ionizing radiation. People whose ancestors lived for long periods in the regions of the globe near the Equator generally have more active melanocytes, and therefore larger quantities of melanin in their skins. This makes their skins dark brown or black and protects them against high levels of exposure to the sun. In areas of the globe closer to the poles, people have far less need for protection from ionizing radiation, so their skin is usually lighter in colour. This allows sunlight to stimulate vitamin D production by the liver. The darker one's skin is, however, the more likely one is to suffer from vitamin D deficiency. Space-filling model of a section of DNA molecule Deoxyribose nucleic acid (DNA) is a nucleic acid that contains the genetic instructions specifying the biological development of all cellular forms of life (and many viruses). ... The equator is an imaginary line drawn around a planet, halfway between the poles. ... Vitamin D is a fat soluble vitamin that contributes to the maintenance of normal levels of calcium and phosphorus in the bloodstream. ...

The most recent scientific evidence indicates that all humanity originated in Africa. As a result, all original people had relatively large numbers of active melanocytes and, accordingly, darker skin. As some of these original tribes of people migrated and settled in areas of Asia and Europe, their melanin production gradually decreased to allow acclimation to climates where radiation from the sun was less intense. It is estimated that this color evolution in an immigrated populace takes approximately 10,000 years to complete. A satellite composite image of Africa Africa is the worlds second-largest continent in both area and population, after Asia. ... World map showing location of Asia A satellite composite image of Asia Asia is the central and eastern part of the continent of Eurasia, defined by subtracting the European peninsula from Eurasia. ... World map showing location of Europe A satellite composite image of Europe Europe is geologically and geographically a peninsula, forming the westernmost part of Eurasia. ... Acclimation is a change occurring in an individual as a result to prolonged exposure of a particular environmental condition, such as a horse shedding its winter coat to produce a lighter summer coat. ... Charles Darwin, the father of modern evolutionary theory In the life sciences, evolution is a change in the traits of living organisms over generations, including the emergence of new species. ...

As with peoples that migrated northward, those with light skin that migrated southward had to acclimate to the much stronger solar radiation. Those people, who produced more skin-protecting melanin, were less likely to suffer from skin cancer, as well as other health problems related to exposure to strong solar radiation, including the photodegradation of certain vitamins such as riboflavins, carotenoids, tocopherol, and folate. In medicine (dermatology), there are several different types of cancer referred to under the general label of skin cancer. ... Solar radiation is radiant energy emitted by the sun, particularly electromagnetic energy. ... Riboflavin (E101), also known as vitamin B2, is an easily absorbed, water-soluble micronutrient with a key role in maintaining human health. ... Carotenoids are organic pigments naturally occurring in plants and some other photosynthetic organisms like algae, some types of fungus and some bacteria. ... Tocopherol, orr Vitamin E, is a fat-soluble vitamin in eight forms that is an important antioxidant. ... Folic acid (the anion form is called folate) is a B-complex vitamin (once called vitamin M) that is important in preventing neural tube defects (NTDs) in the developing human fetus. ...

Most people's skin darkens when exposed to UV light, giving them more protection when it is needed. The closer one lives to the Equator, where the sun's radiation is strongest, the greater the advantage of having high melanin levels in the skin. Dark skin affords far greater protection than fair skin against sunburn and the development of melanoma, a potentially extremely deadly form of skin cancer. Skin cancer, close-up of level IV melanoma Melanoma is a malignant tumour of melanocytes . ...

Higher melanin levels also can be a disadvantage, however, beyond a higher disposition in darker-skinned individuals toward vitamin D deficiency. Dark skin is a complicating factor in the laser removal of port-wine stains. Effective in treating fair skin, lasers generally are less successful in removing port-wine stains in Asians and blacks. Higher concentrations of melanin in darker-skinned individuals simply diffuse and absorb the laser radiation, inhibiting light absorption by the targeted tissue. Melanin similarly can complicate laser treatment of other dermatological conditions in people of color. A port-wine stain or naevus flammeus is a vascular birthmark consisting of superficial and deep dilated capillaries in the skin which produce a reddish to purplish discoloration of the skin. ... The term Asian can refer to something or someone from Asia. ... The term Blacks is often used in the West to denote race for persons whose progenitors, usually in predominant part, were indigenous to Africa. ...

Freckles and moles are formed where there is a greater concentration of melanin in the skin. Freckles are small brownish spots of melanin on human skin in people of fair complexion, predominantly found on the face. ... A mole is a small spot of darkened pigment on the skin, which forms where there is a high concentration of melanin. ...

Albinism is a condition in which an animal (such as a human or a mouse) is incapable of producing melanin, and hence appears white with pink eyes. Albinism is a genetic condition resulting in a lack of pigmentation in the eyes, skin and hair. ... A mouse is a mammal that belongs to one of numerous species of small rodents in the genus Mus and various related genera of the family Muridæ (Old World Mice). ...

Physical properties and technological applications

Melanin is a biopolymer and a neuropeptide. In the early 1970s, researchers found melanin to be an organic semiconductor. Studies revealed that melanin acted as an electrical threshold switch, emitting a flash of light— electroluminescence— when it switched. This knowledge was considered lost for a time, but in 2000, the Nobel Prize in Chemistry was awarded to three scientists for their work in the discovery and development of conductive polymers. The polymers utilized in the research included melanins. A biopolymer is a polymer found in nature. ... A Neuropeptide is any of the variety of peptides found in neural tissue; e. ... An organic semiconductor is an organic substance with low electrical resistance. ... 2000 is a leap year starting on Saturday of the Gregorian calendar. ... Photographs of Nobel Prize Medals. ...

Melanin influences neural activity and mediates the conduction of radiation, light, heat and kinetic energy. As such, it is the subject of intense interest in biotech research and development, most notably in organic electronics (sometimes called "plastic electronics") and nanotechnology. The nervous system of an animal coordinates the activity of the muscles, monitors the organs, constructs and processes input from the senses, and initiates actions. ... Biotechnology is technology based on agriculture, food science, and medicine. ... Organic electronics, or plastic electronics, is a branch of electronics that deals with conductive polymers, or plastics. ... A mite next to a gear chain produced using nanotechnology. ...

Melanin-based bias in human societies

When skin pigmentation as a characteristic of race becomes significant in some way, this phenomenon is known as racialism. Many people and societies overlay racialism with racist perceptions and systems which arbitrarily assign to groups of people a status of inherent superiority or inferiority, privilege or disadvantage based on skin color or racial classification. Apartheid-era South Africa is an example of a white supremacist society based on a system of stratification of power and privilege by skin color, as well as racial admixture. Similar examples can be found in India's caste system; Brazil's highly socially color-stratified society; and, in the U.S., segregation and institutional racism on the part of white-controlled institutions, and internal "color consciousness" on the part some ethnic minorities. Because of the pervasive influence of white supremacist values worldwide, prejudice against people with more highly pigmented skin is the most pervasive form of color bias. Conversely, black supremacy is a far less pervasive phenomenon. Many other societies remain informally divided on the basis of skin color and, often, related ethnicity. (See also colonialism, Nazism and institutional racism.) A race is a distinct population of humans distinguished in some way from other humans. ... Hitlers Nazi Germany: the epitome of 20th-century racialism Racialism is a term used to describe racial policy, in what is generally perceived to be a negative sense, as promoting stratification and inequality between racial categories (in themselves, often disputed). ... An African-American drinks out of a water cooler designated for use by colored patrons in 1939 at a streetcar terminal in Oklahoma City. ... Apartheid (International Phonetic Alphabet or in English and in Afrikaans) is the policy and the system of laws implemented and continued by White minority governments in South Africa from 1948 to 1990; and by extension any legally sanctioned system of racial segregation. ... White supremacy is the variety of white nationalism that believes the white race should rule over other races. ... The word Caste is derived from the Portuguese word casta, meaning lineage, breed or race. ... Racial segregation is a kind of formalized or institutionalized discrimination on the basis of race, characterized by the races separation from each other. ... Institutional racism (or structural racism) is a form of racism that occurs in institutions such as public bodies and corporations, including universities. ... Black supremacy is the belief that blacks as a group are superior to members of other races. ... World map of colonialism circa 1945. ... The Nazi Party used a right-facing swastika as their symbol and the red and black colors were said to represent Blut und Boden (blood and soil). ... Institutional racism (or structural racism) is a form of racism that occurs in institutions such as public bodies and corporations, including universities. ...

Illogical presumptions about people with regard to hair color are far less common than skin-color bias, have far fewer and less serious real-world implications, and are more often applied to women than to men. Common stereotypes in the West are dumb blondes, hot-tempered redheads and vixen brunettes. For alternative meanings for The West in the United States, see the U.S. West and American West. ... One of the worlds most famous blondes Marilyn Monroe, who was in fact a natural brunette Blond (feminine, blonde) is a hair colour found in certain mammals characterised by low levels of the dark pigment eumelanin and higher levels of the pale pigment phæomelanin, in common with red or... Red hair is a hair color shared by several species, among them humans, orangutans and horses. ... Brunette is the feminine of French brunet, which is a diminutive of brun, brune, meaning brown or dark haired, ultimately from Latin BRVNVS (brown). ...

See also

• Black supremacy (see "Melanin Theory")
• Carotene
• Human skin color
• Melanism
• Melanoma
• Organic semiconductor
• Parkinson's disease
• Racism
• Red hair
• Vitamin D