why do we have different coloured eyes

By See also: Eye color often is the genetic trait that fascinates parents the most as a child develops. Will the child's eyes be black, brown, blue, gray, green, hazel or some combination of colors? How a child looks depends on the genetic material each parent contributes to the child. But the parents' genes can mix and match in many different ways. The influences from each parent aren't known until surprise after the child is born! The colored part of the is called the, which has pigmentation that determines our eye color. Human eye color originates with three genes, two of which are well understood. These genes account for the most common colors green, brown, and blue. Other colors, such as gray, hazel and multiple combinations are not fully understood or explainable at this time. We used to think of brown being "dominant" and blue being "recessive. " But modern science has shown that eye color is not at all that simple. Also, eye colors don't come out as a blend of the parents' colors, as in mixing paint. Each parent has two pairs of genes on each. So multiple possibilities exist, depending on how the "Wheel of Fortune" spins. Dutch researchers have announced they are working on ways to determine eye color of adults with sophisticated DNA analysis that can predict with 90 percent accuracy whether people have brown or. In May 2010, the same researchers said they were closing in on the ability to more accurately predict even variable eye colors via DNA analysis and new understanding of how genetics govern eye color. Researchers said these discoveries also have implications for forensic investigations at crime scenes where recovered DNA may give clues about the actual appearance of suspects.

Most babies are born with blue eyes that can darken in their first three years. Darkening occurs if, a brown pigment usually not present at birth, develops with age. Children can have completely different eye colors than either of their parents. But if both parents have, it's most likely that their children also will have brown eyes. The darker colors tend to dominate, so brown tends to win out over green, and green tends to win out over blue. However, a brown/blue parent mix doesn't automatically produce a brown-eyed child. Some children are born with irises that don't match in color. Usually this is caused by faulty developmental pigment transport, local trauma either in the womb or shortly after birth or a benign genetic disorder. Other causes can be inflammation, freckle (diffuse nevus) of the iris and. Having an early is important to make sure nothing serious is going on and "nothing serious" is the most common finding. The iris is a muscle that expands and contracts to control size. The pupil enlarges in dimmer lighting and grows smaller in brighter lighting. The pupil also shrinks when you focus on near objects, such as a book you are reading. When the pupil size changes, the pigments in the iris compress or spread apart, changing the eye color a bit. Certain emotions can change both the pupil size and the iris color. That's why some people say their eyes change colors when they're angry or loving. Eye color also can change with age. This happens in 10 to 15 percent of the Caucasian population (people who generally have lighter eye colors). For instance, my once very brown eyes are now hazel, a combination of brown and green.

However, some
actually get darker with age. Note that if your adult eye color changes pretty dramatically, or if one eye changes from brown to green or blue to brown (called ), it's important to see your. Eye color changes can be a warning sign of certain diseases, such as Fuch's heterochromic iridocyclitis, Horner's syndrome or pigmentary. Ultimately, if you don't like the eye color you inherited, you can always change it with. But remember, even colored contact lenses are a prescription medical device and must be prescribed and monitored by an eye doctor. Don't buy them over the Internet or get them from a friend without having an eye doctor's prescription! If you wear eyeglasses, be sure to choose lenses with. AR-coated lenses eliminate annoying reflections in your glasses that prevent others from seeing the beauty and expressiveness of your eyes. Ask your optician for details and a demonstration. Also, read about that highlight and enhance the color of your eyes and skin tone. [Page updated February 22, 2018] The instance of a person having two differently colored eyes is pretty uncommon, just 11 out of every 1,000 Americans. This uncanny trait is caused by several factors, and can actually develop over time. Iris color develops during the first few months after birth, with the levels of the pigment melanin determining how dark eyes will become. The less melanin expressed in the iris, the lighter a person's eyes look, and vice versa. Sometimes, though, the concentration and distribution of melanin isn't uniform, which leads to a condition known as heterochromia. This condition can present itself in different ways.

There's complete heterochromia, when is a distinctly different color, say, one blue and one brown. Central heterochromia is when the eyes show various colors, such as a blue iris with a golden-brown ring around the pupil. And sectoral heterochromia is when one iris has a splash of color that's different from its overall hue, a trait that actress Kate Bosworth has. Eye pigmentation abnormalities are not necessarily a sign of an underlying health condition. This is known as simple heterochromia, and is generally inherited from a parent. Heterochromia, however, is a common feature of several inherited genetic disorders. For example, Waardenburg syndrome causes children to experience hearing loss, and varying degrees of heterochromia. Another inherited disorder that lists heterochromia as a symptom is neurofibromatosis, which affects the nervous system and causes tumors to form on nerve tissue. Tumor formation inside the eye can cause heterochromia. Irregular iris coloring can also be caused by an injury to the eye, such as a punch leading to bleeding within the eye. An infection or mild inflammation that affects only one eye can cause it, as can the presence of a foreign object in the eye, because that can lead to. Heterochromia can also be caused by glaucoma, which is a group of eye conditions that damage the nerve that carries visual information from the eye to the brain. The sudden onset of heterochromia could be the sign of an underlying medical condition, and a complete eye exam should be conducted by an ophthalmologist to rule out any serious causes. Got a question? and we'll look for an expert who can crack it.

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