Oculocutaneous albinism is a form of
albinismAlbinism is a form of hypopigmentary congenital disorder, characterized by a partial or total lack of melanin pigment in the eyes, skin and hair, or more rarely...
involving the
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
s ("oculo-"),
skinThe skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system made up of multiple layers of mesodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. Skin of a different nature exists in amphibians, reptiles, birds...
("-cutaneous"), and according to some definitions, the
hairHair is a protein filament that grows through the epidermis from follicles deep within the dermis. The fine, soft hair found on many nonhuman mammals is typically called fur; wool is the characteristically curly hair found on sheep and goats. Found exclusively in mammals, hair is one of the...
as well.
Oculocutaneous albinism is a form of
albinismAlbinism is a form of hypopigmentary congenital disorder, characterized by a partial or total lack of melanin pigment in the eyes, skin and hair, or more rarely...
involving the
eyeEyes are organs that detect light, and send electrical impulses along the optic nerve to the visual and other areas of the brain. Complex optical systems with resolving power have come in ten fundamentally different forms, and 96% of animal species possess a complex optical system...
s ("oculo-"),
skinThe skin is the outer covering of the body. In humans, it is the largest organ of the integumentary system made up of multiple layers of mesodermal tissue, and guards the underlying muscles, bones, ligaments and internal organs. Skin of a different nature exists in amphibians, reptiles, birds...
("-cutaneous"), and according to some definitions, the
hairHair is a protein filament that grows through the epidermis from follicles deep within the dermis. The fine, soft hair found on many nonhuman mammals is typically called fur; wool is the characteristically curly hair found on sheep and goats. Found exclusively in mammals, hair is one of the...
as well.
Four types of oculocutaneous albinism have been described, all caused by a disruption of
melaninMelanin is a class of compounds found in plants, animals, and protists, where it serves predominantly as a pigment. The class of pigments are derivatives of the amino acid tyrosine. Many melanins are insoluble salts and show affinity to water...
synthesis and all autosomal recessive disorders.
Types
| Name |
OMIM |
Gene |
Description |
|
| OCA1 >
| TYRTyrosinase is an enzyme that catalyses the oxidation of phenols and is widespread in plants and animals...
|
tyrosinaseTyrosinase is an enzyme that catalyses the oxidation of phenols and is widespread in plants and animals...
gene, and can occur in two variations. The first is OCA1a, and means that the organism cannot develop pigment at all. The hair is usually white (often translucent) and the skin very pale. Vision usually ranges from 20/200 to 20/400. The second is OCA1b, which has several subtypes itself. Some individuals with OCA1b can tan and also develop pigment in the hair. One subtype of OCA1b is called OCA1b TS (temperature sensitive), where the tyrosinaseTyrosinase is an enzyme that catalyses the oxidation of phenols and is widespread in plants and animals...
can only function below a certain temperature, which causes the body hair in cooler body regions to develop pigment (i.e. get darker). (An equivalent mutation produces the coat pattern in Siamese catsThe Siamese is one of the first distinctly recognised breeds of Oriental cat. The exact origins of the breed are unknown, but it is believed to be from Southeast Asia, and is said to be descended from the sacred temple cats of Siam ....
.) Another variant of OCA1b, called Albinism, yellow mutant type is more common among the AmishThe various Amish or Amish Mennonite church fellowships are Christian religious denominations that form a very traditional subgrouping of Mennonite churches. They are best known for their simple living, plain dress and resistance to the adoption of many modern conveniences...
than in other populations, and results in blonde hair and the eventual development of skin pigmentation during infancy, though at birth is difficult to distinguish from other types. About 1 in 40,000 people have some form of OCA1.
|-
| OCA2 |
| OCA2 P protein is a protein that in humans is encoded by the OCA2 gene.OCA2 encodes the human homologue of the mouse p gene. The P protein is believed to be an integral membrane protein involved in small molecule transport, specifically tyrosine - a precursor of melanin...
|
phenotypeA phenotype is any observable characteristic or trait of an organism: such as its morphology, development, biochemical or physiological properties, or behavior. Phenotypes result from the expression of an organism's genes as well as the influence of environmental factors and possible interactions...
(appearance): yellow hair, pale skin, and blue, gray or hazel eyes. About 1 in 15,000 people have OCA2. The gene MC1R doesn't cause OCA2, but does affect its presentation.
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| OCA3 |
| TYRP1 Tyrosinase-related protein 1, also known as TYRP1, is an enzyme which in humans is encoded by the TYRP1 gene- Function :Tyrp1 is a melanocyte-specific gene product involved in melanin synthesis. Mouse Tyrp1 possesses dihydroxyindole carboxylic acid oxidase activity, The function in human...
|
rufous oculocutaneous albinism (ROCA or xanthism) . The incidence rate of OCA3 is unknown.
|-
| OCA4 |
| SLC45A2 Membrane-associated transporter protein is a protein that in humans is encoded by the SLC45A2 gene.-Further reading:...
|
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