How do children inherit eye color? Is it possible to predict what the child will have? Why are they pink in albinos? If both parents have brown eyes, can a blue-eyed baby be born to them? How is the color of the iris formed? These questions are relevant at all times. The answer to them is contained in the totality of internal and external characteristics of the body, formed on the basis of the genotype, as well as acquired as a result of individual development. What does this mean and what does the eye color of a person depend on?
This characteristic is determined by the pigmentation of the iris (iris), consisting of the ectodermal (posterior) and mesodermal (anterior) layers. That is, the human eye color depends on the nature of the distribution of fuscin (it contributes to the production of visual pigment, absorbs light and prevents its scattering and reflection, as a result, the clarity of visual perception of the image improves) in the pigment cells of the back layer and melanin (a natural dark substance) in pigment-containing and reflective cells (chromatophores) of the anterior layer. The color is also affected by the state of the vessels and fibers of the iris, the different amount and nature of the pigment, which, in turn, is determined by genetics. Eye color is due to genes. But not all of them have been studied.
Melanin is a colored substance, it affects not only the color of the eyes, but also the hair and skin tones. Still, what does eye color depend on? The more melanin is contained in the mesoderm layer, the darker the iris, and the less it is distributed in the pigment cells of the anterior layer of the iris, the brighter it will be. There are brown and black melanin (or eumelanin), as well as yellow (or pheomelanin). Certain genes are responsible for the nature and quantity of this natural substance and its distribution. As a result, the color of the iris can be blue, blue, gray, green, amber, swamp, brown or black. The child will inherit the resemblance to a parent with dominant traits (brown, light brown and green) and will not get the color of the parent's eyes with recessive traits (blue or gray).
In blue eyes, the back layer is colored blue due to vessels formed by collagen fibers, the front layer is characterized by a minimum content of melanin. Blue ones differ from blue ones in higher density of whitish fibers: the higher their density, the brighter the iris. The gray color of the eyes is explained by an even greater collagen density. In the front layer of greens there is a small amount of melanin, due to the blue color of the back layer, the iris is heterogeneous green and of different shades. What determines the color of amber eyes? The lipofuscin pigment ensures their uniform color. With a moderate content of melanin in the outer shell of the eyes become marshy or hazel. Hazel occurs when chromatophores contain a lot of melanin. Black is characterized by a high content of this pigment, which completely absorbs light. In albino, it is absent, and the iris appears pink or red due to the reflection of the color of blood vessels.
Newborns have a blue iris, but it may darken over the next few years. What explains this and what determines the color of the eyes of the child? Melanin in the body by the time of birth is not produced in the fetus, since until that time protection from ultraviolet rays, which is performed by dark pigment, was not required. Its main purpose is to prevent radiation damage to body tissues. After birth, the production of melanin begins by specialized cells (melanocytes). Therefore, the true color of the eyes of a child can be determined no earlier than three years, although changes sometimes occur before 10-12 years. In adults, the color of iris can also change under the influence of drugs or due to poor health. For example, a yellowish color appears due to the accumulation of lipofuscin.
Brown eyes are usually considered dominant, while blue eyes are recessive. But modern science has proved that everything is not so simple. The darker the color, the more it dominates: brown over green, green over blue. But not always the child will be brown-eyed if the iris of mom and dad is brown. In children, it may be different. This is usually caused by an abnormal development of pigment transport, local injuries or in the womb, or shortly after birth, as well as a genetic disease.