The former is more likely than the latter. These variations can result in blue-eyed parents having a brown-eyed child, or brown-eyed parents having a blue-eyed child. These genes can raise or lower melanin levels, causing a child to have more or less melanin than either parent. Although nearly 75 percent of eye color is controlled by the OCA2 gene, other genes provide a pathway for melanin. When less protein is produced, the eyes receive less melanin and eye color leans toward the blue end of the spectrum. If more protein is produced, then the eyes received more melanin, and eye color leans toward the brown end of the color spectrum. The OCA2 gene (formerly called the P gene) provides instructions for producing the P protein located in the melanocytes (specialized cells that produce melanin). The OCA2 and HERC2 genes are located in this region. A region on chromosome 15 has a big part in determining eye color. Differences in the copies received from each parent causes variations in the amount of melanin produced. The chromosomes a child inherits carry genetic information that determines eye color. Eyes with no melanin on the front layer of the iris scatter light so that more blue light reflects out, so that the eyes appear blue. People with brown eyes have melanin on the back layer of the iris and some on the front layer, which absorbs more light and causes the iris to look brown. The difference in eye colors is due to the concentration and location of the brown melanin on the two layers of the iris. All eye colors have the same brown melanin incapable of refracting light. In eye color, there isn’t blue or green pigment. Genetic makeup determines the amount of melanin in the eye.

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Learn more about the genetics of eye color, including: Although eye color is determined by genetic makeup, variations can cause different shades to appear.

Know Your Health: Genetics of Eye ColorĮye colors have evolved over time and have roots in our ancestry. However, a genetic variation can cause a child’s eye color to be unpredictable, resulting in two blue-eyed parents having a brown-eyed child. With minimal levels of the same brown melanin, the eyes look blue.

With high levels of brown melanin, the eyes look brown. A parent’s genetic makeup determines the amount of pigment, or melanin, in the iris of the his or her child’s eye. Whether eyes are blue or brown, eye color is determined by genetic traits handed down to children from their parents. Learn about the genetics of eye color in this guide. Eye colors are passed down through generations, but sometimes genetic variations can lead to surprising results in eye colors.

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