Learn more about the genetics of eye color, including:. Genetic makeup determines the amount of melanin in the eye. All eye colors have the same brown melanin incapable of refracting light. The difference in eye colors is due to the concentration and location of the brown melanin on the two layers of the iris. 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.
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. The chromosomes a child inherits carry genetic information that determines eye color. Differences in the copies received from each parent causes variations in the amount of melanin produced.
A region on chromosome 15 has a big part in determining eye color. The OCA2 gene formerly called the P gene provides instructions for producing the P protein located in the melanocytes specialized cells that produce melanin. If more protein is produced, then the eyes received more melanin, and eye color leans toward the brown end of the color spectrum.
When less protein is produced, the eyes receive less melanin and eye color leans toward the blue end of the spectrum.
Although nearly 75 percent of eye color is controlled by the OCA2 gene, other genes provide a pathway for melanin. These genes can raise or lower melanin levels, causing a child to have more or less melanin than either parent. These variations can result in blue-eyed parents having a brown-eyed child, or brown-eyed parents having a blue-eyed child.
The former is more likely than the latter. Each cell in the human body normally contains 23 pairs of chromosomes. Chromosome 15 likely contains to genes integral to producing proteins. The presence of at least one genetic variation in the HERC2 gene can reduce the amount of melanin produced, leading to lighter eyes.
Eye color was once thought to be the result of a single hereditary trait. It was thought that each person received one eye color gene from each parent, and the dominant gene determined eye color. In this model, the brown-eye color gene was always dominant over the blue-eye color gene, and only two blue-eye color genes could color eyes blue. Charles and Gertrude Davenport developed the dominant brown eye model in They suggested that blue eyes were caused by a single recessive gene, and blue-eyed parents could never produce a brown-eyed child.
Dominant and recessive genes refer to inheritance patterns, and describe how likely it is for a certain trait to pass from parent to offspring. Today, we know this model is simplistic, and that many genes determine that eye color. While it is possible to predict the probability of eye color, genetic factors may alter the outcome. With eye color controlled by more than one gene, it is possible for a newborn to inherit any eye color.
Predicting eye color is further complicated because it sometimes changes after birth. According to one theory, almost everyone This is based on the DNA analysis of about blue-eyed people, in which only one person did not have the same blue-eye genetic mutation as the rest of the group.
This mutation seems to have occurred during the Neolithic period or New Stone Age during the great agricultural migration to the northern part of Europe. A previous Biotech article that provides an overview of comparative genomics can be found here. Eye color genes In humans, eye color is determined by the amount of light that reflects off the iris, a muscular structure that controls how much light enters the eye. Blue eyes contain minimal amounts of pigment within a small number of melanosomes.
Irises from green—hazel eyes show moderate pigment levels and melanosome number, while brown eyes are the result of high melanin levels stored across many melanosomes see figure two, left. To date, eight genes have been identified which impact eye color. OCA2 produces a protein called P-protein that is involved in the formation and processing of melanin.
Individuals with OCA2 mutations that prevent P-protein from being produced are born with a form of albinism. These individuals have very light colored hair, eyes and skin. Non-disease-causing OCA2 variants alleles have also been identified. The allele that results in high levels of P-protein is linked to brown eyes. Another allele, associated with blue eye color, dramatically reduces the P-protein concentration. However, while about three-fourths of eye color variation can be explained by genetic changes in and around this gene, OCA2 is not the only influence on color.
A recent study that compared eye color to OCA2 status showed that 62 percent of individuals with two copies of the blue-eyed OCA2 allele, as well as 7.
The genetic tests for these codes is extensive. If you are interested in our gender selection program and are ready to enroll in gender selection, we may also have options for you to bring down the cost of initial screening to see if you are candidates to select eye color.
Please click here to view a graph outlining the chances of having a baby with a chosen eye color based on your own eye colors. We encourage you to call us for more information. For current pricing for both the eye color genetic screening first step and the actual eye color selection procedure, please email or call us at or We are pleased to announce that we are once again taking reservations from parents interested in screening their embryos for genetic health, gender and eye color.
We are predicting our updated and highly accurate screening technology to be app. Program participation requires that parents be screened genetically to determine if they carry the genes to produce a child with the eye color they seek.
Call today for information: or Written by Dr. Thank you for your interest in our Eye Color Selection service. Please use the form below to receive your free information packet to help answer any questions you may have about enrollment.
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