Facts About the Iris in Your Eye

The Iris
••• Image by Flickr.com, courtesy of Howie Le

The iris of your eye is a circular membrane that is able to contract or expand the pupil in order to let light into the interior of the eye. It is available in three main colors--blue, green and brown--determined by the two genes that are inherited from the parents.

Identification

The iris of your eye is the circular, colored membrane that surrounds the pupil.

Color

Colors of the iris include brown, blue, green, hazel and, in cases of albinos, red. Eye color is determined by the amount of melanin in the eye, the inherited genes and the age of the person, as humans under the age of 3 are still producing eye pigments.

Function

The iris regulates the amount of light that enters the eye by opening and closing the pupil. In low light levels, the iris opens, dilating the pupil, and in high light levels, the iris contracts, blocking the amount of light which enters the eye.

Location

The iris of your eye is located behind the cornea, which is the outer layer of the eye, and in front of the lens.

Genetics

Humans inherit two copies of the gene for eye color, one from each parent. Brown is the dominant gene, which means the person may have two brown genes, or one brown gene and one blue or green gene. Blue-eyed people can only have two copies of blue genes, and green-eyed people can have either two copies of green or a copy of green and blue. Albinos have no melanin in their eyes, causing their irises to appear red.

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