2006-10-01 17:46:35 · 4 answers · asked by Anonymous in Science & Mathematics ➔ Biology
Eye color or eye colour is a polygenic trait and is determined by the amount and type of pigments, primarily melanin, present in the eye's iris. Although there seem to be three genotypic eye colors (brown, green, and blue), humans and other animals have many phenotypic variations in eye color. These variations in color are attributed to varying ratios of eumelanin and pheomelanin produced by melanocytes in the iris.
Three main elements within the iris contribute to its color: the melanin content of the iris pigment epithelium, the melanin content within the iris stroma, and the cellular density of the iris stroma. In eyes of all colors, the iris pigment epithelium contains the black pigment, eumelanin. Color variations among different irises are typically attributed to the melanin content within the iris stroma. The density of cells within the stroma affects how much light is absorbed by the underlying pigment epithelium.
Eye color is an inherited trait influenced by more than one gene. Although it was once thought that brown eye color was always dominant and blue eye color was always recessive, the fact that two blue-eyed parents can give birth to a brown-eyed child has shown that the determination of eye color does not follow the simple rules of Mendelian inheritance. Three gene pairs coding for human eye color are currently known: EYCL1, EYCL2, and EYCL3.
As melanin production generally increases during the first few years of life, the blue eyes of some babies may darken as they get older. Eye color typically stabilizes by 6 years of age.
2006-10-01 17:53:48 · answer #1 · answered by prakash s 3 · 1⤊ 0⤋
What Causes Hazel Eyes
2016-11-11 05:37:32 · answer #2 · answered by ? 4 · 0⤊ 0⤋
My son has hazel eyes and they tend to change with his mood so I'm guessing some type of horomone or temperature variant. As far as different eye colors......genes, baby!
2006-10-01 17:54:48 · answer #3 · answered by It's Been Cool 2 · 0⤊ 0⤋
my boyfriend has hazel eyes that can change colour dramatically, ranging from light aquamarine to near-black brown. it generally changes with his mood (light when happy, dark when angry). what i've noticed is that there is more bluey-green near the outside of his iris, and there is a ring of brown just around his pupil. so i'm speculating that these rings of colour stretch differently when his moods change, so that one is more prominant than the other. how this happens, i have no clue!
eye colour varies from person to person because everybody has a different amount of melanin in their iris (pigmented molecules). melanin also controls the colour of our skin. the more melanin you have, the darker you are, and vice versa. birthmarks are just concentrated spots of melanin. we also have freckles in our eyes, which are also concentrated spots of melanin. we inherit different eye colours from our parents, and our eye colour depends on the eye colour alleles (or genes) that they have.
2006-10-01 18:04:30 · answer #4 · answered by wildcat 3 · 0⤊ 0⤋
i dunno..maybe the moon or the weather..my eyes change color too...mine are sort of green yellow flecks of orange as well...and there always changing slightly from one day to the next...wierd and wonderfull...better than boring same color eyes that never change hey? !!
2006-10-01 17:50:13 · answer #5 · answered by free-spirit 5 · 0⤊ 0⤋
Richard Lee and Mike Williams posted the same question. You should read their answers side by side.
2016-08-23 07:59:21 · answer #6 · answered by ? 4 · 0⤊ 0⤋
Genetic modification.
2006-10-01 17:55:29 · answer #7 · answered by ag_iitkgp 7 · 0⤊ 0⤋
I was interested to know this as well
2016-08-08 16:17:15 · answer #8 · answered by ? 3 · 0⤊ 0⤋