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Color of Iris
The iris is usually strongly pigmented, with colors ranging from brown to green, blue, gray and hazel. From time to time, the color is due to a lack of pigmentation, as in white and pink oculo-cutaneous, or the concealment of the pigment of the blood vessels, like the red one abnormally vascularised iris (although human albinos generally have very light blue eyes, just like how the non-human iris pigment color blue).
Despite the large numbercolors, there is only one pigment that contributes substantially to normal human iris color, melanin, the dark pigment. Structurally, this huge molecule is only slightly different from its equivalent found in skin and hair.
Genetic and physical factors, the color of the iris
Iris color is a very complex phenomenon, a combination of texture, pigmentation, connective tissue and blood vessels within the iris stroma, which together with avarious epigenetic constitution. A person who "eye color" is actually the color of the iris, the cornea is transparent and the white sclera entirely outside the zone of interest. This is a common misconception that the iris color is entirely due to its melanin pigment, but depends only from brown to black.
Melanin is yellowish brown to dark brown and black pigment cells in the stroma of the iris pigment epithelium, which in a thin but very opaque on liesBack to the iris. Most human iris also show a condensation of melanin in brown stromal thin anterior margin, which through its influence on color overall open position.
The degree of dispersion of melanin, which in subcellular bundles called melanosomes, has some influence on the observed color, but melanosomes in the iris of humans and other vertebrates are not mobile and the degree of dispersion of the pigments can not be undone.
Aggregation of abnormalNot occur in melanosomes disease and cause irreversible changes in iris color (heterochromia see below). Colors other than brown or blacks are due to selective reflection and absorption of other stromal components. Sometimes lipofuscin, a yellow "wear and tear" pigment occurs in the color visible to the eye, especially in older or diseased green eyes (but) in healthy subjects and green eyes of the people.
Blue is one of the possible eye colors in humans. The "blue" alleleothers in Bey2 and Gey genes of chromosome 15 is recessive. This means that both alleles of both genes not blue blue-blue must have "in which a person with blue eyes. If one of the alleles are not green and blue "(" for Gey or "brown" for Bey2), then the person would have those colored eyes respectively.
Or as one allele (if not both) may be transmitted to offspring, it is entirely possible that someone might have passed the no-blue-eyed, blue-eyed children. Because of the recessiveNature, which is a certainty if both parents have blue eyes. Although this statement gives an idea of defining the color of eyes, is incomplete, and all factors of eye color and its changes are not fully understood.
Faking the iris color
Some eye colors are sometimes to be particularly attractive and the reason for expressing contact lenses can be worn for a fancy natural eye color with another. Are rarenecessary, and almost never recommended by serious medical, unless the patient needs further protection for the retina, as in aniridia.
After the introduction of machines that can automatically scan their iris pattern, and their use in some airports as a security measure, it is reported that some people, colored contact lenses, or deliberate iris injury with lasers used to prevent 'personal identification.
Iris color as paternity test
As mentioned above, even ifThere has been much ado about the search for genes for eye color, there are no simple genetic determinism for such a complex function, because there is no longer the eye color pigmentation. Overall, there are no simple Mendelian inheritance in rainbow colors. Consequently, no serious test of paternity can be based on observations or measurements of the colors of the rainbow, but we note that blue eyes are normally phenotypically recessive, so that a child of two brown eyes blue-eyed parents can create someDoubts about the paternity.
Different colors in the two eyes
Heterochromia (also known as a heterochromia iridis or heterochromia iridium) is an eye disease in which the iris is a different color from the other iris (complete heterochromia), or when the iris is part of a different color than the remainder (partial heterochromia or sectoral heterochromia).
Not common in humans, is often an indicator of eye diseases such as chronic iritis or diffuse irisMelanoma may also occur as a normal variant. Sectors or patches of strikingly different colors in the iris that are less common. Alexander the Great and Anastasios The first ones were synchronized (dikoros "with two pupils") heterochromias for their patent. In his case, this was not a true Dicorato (two students of the same iris). Polycoria Real is due to illness, but is more often due to previous injury or surgery.
In contrast, heterochromia, and iris color models in commonveterinary practice. Siberian Huskies show heterochromia from inbreeding, perhaps analogous to the genetically determined Waardenburg syndrome of humans.
Some white cat loves) (eg, white Persians may show striking heterochromia, with the most common model is a blue uniform, the other green. Striking variegation within the same iris is also common in some animals, and the standard is somehow.
Breeding of different races, especially those with a coat of blue merle(such as Australian Shepherds and Border Collies) may show well-defined blue areas within a brown iris as well as separate blue and dark eyes. Some horses (usually within the white, spotted, or Isabella Palomino able to show groups of breeds), yellow, brown, white and blue all the same eye, without any sign of eye disease.
Eye with a white or bluish-white iris is also known as Zander
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