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Eye colors and their inheritance are associated with the eye colors of ancestors, not necessarily of the parents themselves. Depending on the classification, you can distinguish from 16 to 80 variants of eye color for future generations. The color of the eyes depends on melanin, a pigment that is also present in the skin. What eye color is dominant and which is very rare?
Eye colors and melanin
The black pigment, i.e. melanin, and the variables of the dark brown pigment, i.e. eumelanin, and the red pigment, i.e. pheomelanins, affect the eye color in humans. The different content of these pigments in the iris epithelium and in the stroma of the iris determines the color of the eyes. The concentration of the stromal cells of the iris is also important, as it determines how much light is absorbed by the melanin of the iris epithelium. The more melanin a person has, the darker their skin complexion, the darker the color of their eyes and the darker their hair. Brunettes and dark-eyed lockers have a lot of melanin, more than blondes and redheads. In addition, melanin absorbs ultraviolet rays. Albinos who are deficient in melanin are not immune to this radiation.
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Eye colors – genetics
The color of our iris does not only depend on the color of the parent’s iris. We inherit from our ancestors, not only from our father and mother. The color depends on the set of genes and can change. Newborns and infants have light blue eyes. After a few months, this color often changes to brown or green. Then stronger pigments are released and the eye color changes.
School genetics make it clear that when a mother and father have blue eyes, their offspring cannot have brown eyes. Hazel eyes are passed on by the dominant gene, blue by the recessive gene. Two recessive genes cannot produce a dominant gene.
A specialist in the field of clinical genetics at NZOZ Genomed in Warsaw, Dr. Krystyna Spodar, MD, PhD (www.nzoz.genomed.pl) explains why this is not true and parents with blue eyes may have offspring with brown eyes: – In fact eye color is determined by the amount of melanin (black pigment) and the ratio of eumelanin (dark brown pigment) to pheomelanin (reddish pigment). The OCA2 and HERC2 genes play the most important role in determining the color of the irises, but apart from those mentioned, there are at least 10 other genes known to influence this trait. Ultimately, the interaction of all these genes determines the final result.
Thus, the eye colors from their parents, if both are blue, do not prejudge the appearance of hazel ones.
Eye colors – as a percentage
There are three areas of the chromosome in the human genotype that are responsible for eye color, these are EYCL1, EYCL2 and EYCL3, which are responsible for three eye colors: brown, blue, green. If all 3 genes determine the same color, then the color of the eyes is clear, if this is not the case, a mixed color appears, that is, hazel – a combination of brown and green, gray – a combination of blue and green.
Eye colors are sometimes difficult to distinguish because they depend on many factors such as light, ambient shade, the same color can be seen differently. The color palette of human eyes consists of a multitude of brown and blue colors. That is why there are many variations of eye color. In general, brown is considered the dominant color (90% of people in the world have eyes of various shades of brown), then 7%. of people in the world are people with blue eyes, gray eyes are only 2 percent. population, and 1 percent. she has green eyes. The green color is therefore the rarest.
1 percent of the population suffer from heterochromia, which is a birth defect in which one or both eyes are unevenly colored. The person who develops heterochromia may have one blue eye and the other a brown or purple ring on the hazel iris. Fortunately, this defect does not cause any complications in the eye, it is not a typical eye defect, it is not bothersome, only visible.
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