Genetics On Eye Color

 Genetics on Eye Color

The color of the eyes comes from the iris, specifically from a layer called the stroma. The main pigments that contribute to eye color are melanin, pheomelanin, and eumelanin. Melanin is a yellow-brown pigment that also affects skin tone. Pheomelanin is a red-orange pigment found in people with green or hazel eyes. Eumelanin is a dark brown or black pigment that deepens eye color. These combinations of pigments determine whether a person's eyes appear brown, hazel, green, or blue.

A baby's eye color can change over time, especially during the first year of life. Some babies are born with blue or gray eyes, while others are born with brown eyes. This depends on their genetic background and the amount of pigment present. Pigment production increases during the first six months after birth, and a child’s eye color may not be fully established until around one year of age.

Eye color is influenced by the genes OCA2 and HERC2. These genes control how much pigment is produced and how it is distributed in the iris. Each person inherits two alleles for each gene—one from each parent. If the alleles differ, the dominant one is expressed. Brown eyes tend to be more dominant than blue eyes. Researchers also believe that people with blue eyes may share a distant common ancestor.

It is still possible for two blue-eyed parents to have a child with brown eyes. This can happen because parents may carry hidden genetic variants for brown eyes that can be passed down to their child. Punnett squares can help estimate probabilities based on the parents’ traits, but they are not always reliable because they do not account for how many genes are involved.

In some cases, unusual eye color can provide clues about a person’s health. For example, Waardenburg syndrome can cause heterochromia, a condition in which a person has two different-colored eyes, and it may also be linked to hearing loss. Another condition, ocular albinism, results in very pale blue eyes due to a lack of pigment and is more commonly seen in males.

Source: https://www.verywellhealth.com/genetics-of-eye-color-3421603

Extra Source: https://www.sciencenewstoday.org/the-genetic-secrets-behind-eye-color