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Genetics and Eye Color

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Eyes are extremely advanced and beautiful organs. It is amazing how many different shades and color combinations there can be of the iris. Many people wonder, what determines one’s eye color, what role do genes play in determining eye color and how does it work? Eye color is a result of the pigmentation of the iris, the circular part of the eye surrounding the pupil.

Pigmentation of the iris ranges on a color spectrum of very light blue to dark brown. Darker eye colors are typically due to higher levels of melanin pigment in the iris, while lighter eye colors are due to the stroma, which is a layer of the iris that creates an effect which is called scattering of light. Most of the time you will hear people identify eye color into four different categories, blue, green, hazel, or brown. Although occasionally, people will categorize eyes in the grey spectrum. Usually, hazel a combination of green and brown. Generally, those with lighter eye colors, such as green and blue, come from a line of European ancestry.

How genes compose eye color

A while ago, it was thought that eye color was determined by one simple gene. The recessive gene being blue, and the dominant gene being brown. It was believed that parents who both had blue eyes could not have a child born with brown eyes. Later studies found that this is untrue, and although uncommon, it is possible for parents with the same colored eyes to have a child with different colored eyes. It is now known that eye color is a polygenic trait, which means that it is determined by multiple genes. There are 46 specific chromosomes received from the parent, these output into 23 pairs. These chromosomes are made of genes which hold the DNA. Two of the major genes that are responsible for the production of melanin is contained in chromosome 15.

The two major genes responsible

The two major genes responsible that are located in chromosome 15, are the OCA2, and the HERC2 gene. The OCA2 gene, is also known as the P protein gene, is a part of the process of the maturation of melanosomes. Melanosomes are cellular structures that work to generate and store melanin. The P protein plays a big part in the quantity as well as the quality of the melanin that becomes present in the iris. There are certain polymorphisms in the OCA2 gene that can reduce the amount of relevant P protein, where less of the P protein equals less melanin in the iris, which then leads to blue eyes instead of brown.

There is a part of the HERC2 gene, called the intron 86, that holds a piece of DNA that is in charge of the expression of the OCA2 gene. There is a polymorphism in this region of the HERC2 gene that can cause a reduction of the expression of the OCA2 gene, which in turn leads to less melanin in the iris and therefore creates for lighter-colored eyes.

The eyes are complicated and beautiful organs, and it is important that you do your best to take care of them. Regularly seeing your doctor for an eye exam in Arlington is key for maintaining eye health. Here at First Eye Care, we are a highly recommended and trusted vision center that has you and your family’s visual health as a first priority. Contact us today to make an appointment.

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