Iris color
The iris is usually strongly pigmented, with colors ranging from brown to green, blue, gray and hazel. On the occasion of his color is due to the lack of pigmentation, as in the white rose of oculocutaneous albinism, or darkening of the pigment of the blood vessels, like the red iris abnormally vascularized (although human albinos generally have very small eyes blue iris pigmented no man is a pale blue).
Despite the wide range of colors, there is only one pigment that contributes substantially to the normal color of the iris of man, the black pigment called melanin. Structurally, this molecule is enormous slightly different from its counterpart in the skin and hair.
Genetic and physical factors determining iris color
Iris color is a very complex phenomenon, which is the combined effect of texture, pigmentation, fibrous tissue and blood vessels in the iris stroma, which together form the constitution of an individual's epigenetics. "Eye color" a person is actually the color of the iris, cornea and sclera is transparent completely white outside the area of interest. It is a common misconception that the iris color is entirely due to its melanin pigment, but it only varies from brown to black.
Melanin is yellowish-brown to dark brown in the stromal cells of pigment and black pigment in the epithelium of the iris, which is in a thin but very opaque in the back of the iris. Most human irises also show a condensation of brown melanin in the stroma at the thin edge, which by its position clearly influences the overall color.
The degree of dispersion of melanin, which is in subcellular bundles called melanosomes, has some influence on the observed color, but melanosomes in the iris of man and other vertebrates are not mobile, and the degree of pigment dispersion can not be reversed.
abnormal aggregation of melanosomes occurs in the disease and can cause irreversible changes in iris color (see heterochromia, below). Colors other than brown or black are due to selective reflection and absorption of other components of the stroma. Sometimes lipofuscin, a yellow "wear and tear" pigment also enters the visible eye color, especially in elderly or green eyes (but not the health of man's green eyes.)
Blue is one of the colors of the eyes in humans. The "blue" allele, existing in Bey2 Gey genes of chromosome 15, is recessive. This means that both genes must have both blue alleles namely "Blue-blue", a person with blue eyes. If one of the alleles are "blue" ("green" for Gey or "brown" to Bey2) then the person would have colored eyes respectively.
Whether as allele (but not both) can be transmitted to offspring, it is perfectly possible that someone who has blue eyes not to have children with blue eyes. Due to its recessive nature, is a certainty if both parents have blue eyes. While this explanation gives an idea of the division color of eyes, incomplete, and all factors that contribute to eye color and its variations are not fully understood.
Faking the iris color
Some eye colors are sometimes seen as especially attractive and motif expressing contact lenses can be used to mask the natural color eyes with another. They are rarely needed and almost never recommended by serious practitioners, unless the patient's retina needs extra protection, as in aniridia.
Since the introduction of machines that can automatically analyze the patterns of the iris, and its use in some airports as a security measure, it is reported that some people have resorted to colored contact lenses, or deliberate iris injury with lasers, to avoid identification.
Iris color proof Paternity
As indicated above, although there was much talk about the discovery of genes for eye color, there is no simple genetic determinism for a complex trait, because there is more to iris color pigmentation. In general, there is no simple Mendelian inheritance of iris color. Consequently, no serious test of paternity can be based on observations or measurements of iris color, except to note that blue eyes are normally phenotypically recessive, so a brown-eyed boy two blue eyed parents can raise doubts about paternity.
The different colors in both eyes
Heterochromia (also known as rubeosis heterochromia or heterochromia iridium) is an eye condition in which one iris is a different color from the other iris (complete heterochromia), or when the iris is part of a different color from the rest (partial heterochromia or sectoral heterochromia).
Rare in humans, it is often an indicator of eye disease as chronic iritis or diffuse iris melanoma, but may also occur as a normal variant. Sectors or patches of strikingly different colors in the same iris are less common. Alexander the Great and Anastasios first doubled (dikoros "with two pupils") for patent heterochromia. For them, there was a real dicoria (Two students in the same iris). real polycoria may be due to an illness, but is more often due to trauma or previous surgery.
By contrast, heterochromia iris and varied patterns are common in veterinary practice. Siberian Husky show heterochromia due to interbreeding, possibly similar to Waardenburg syndrome genetically determined in humans.
Some white cat fancies (eg, white Persians) may show striking heterochromia, with the most common pattern is a blue uniform and a green. Variegation achieve the same iris is also common in some animals, and is the norm in some species.
Several herding breeds, including blue merle color dress (like Australia and Shepherds Border Collies) may show well-defined blue areas within a brown iris as well as separate blue eyes and darker. Some horses (usually white, palomino seen Cremello or groups of breeds) may show amber, brown, white and blue, all in the same eye, without any sign of eye disease.
An eye with an iris white or bluish white is also known as Alaska
Related Resources:
To learn more about a breakthrough permanent eye color surgery, please visit http://newcoloriris.com for more information and to learn more about an alternative to contacts.
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