Mendelian traits in humans.. Different eye color because of the different composition of the iris and the amount of melanin

Mendelian traits in humans:

As in the case of (earlobe - the color of the eye - the form of thumb - the ability to bend the tongue)

The inheritance of eye color in humans:

Eye color difference due to the difference in the installation of the iris and the amount of melanin pigment.

Eye color nuances (Brown - Black - hazel ..) prevailed and blue eyes.

Why then the light color of the eye?

Scientists suggest that the reason behind this is a change resulting from the existence of a common ancestor that had a change in one of the genes that control melanin production. It is believed that this change or transformation caused a decrease in melanin production in the iris.

Therefore, the color of some eyes appears blue, green, or hazelnut in color, and the reason here is not the presence of a variety of color pigments, but rather the weakness of the melanin pigment. And when the melanin pigment in the eye is weak, the absorption of light is less. This means that the extra amount of light diffuses out of the iris and as it diffuses, the light is reflected differently from the color of the light spectrum. Therefore, the lack of melanin in the eyes gives them a blue color. And if the percentage of melanin increases slightly, the eye color becomes green or hazel.

There are several genes that determine eye color

Scientists thought that there was only one type of gene responsible for eye color. However, recent research has shown that there are approximately 16 different types of genes that could be responsible for determining eye color. This explains how two parents with the same eye color have a child with a different eye color.

When a baby is born, his eyes appear blue because the melanin pigment is still developing. Until he reaches the age of one year, the cells begin to form, that is, when the melanin pigment accumulates in the iris and makes the eye color darker.

Eye color varies in light of the climatic difference.

The melanin pigment present in the eyes, hair and skin acts as a protection against the harmful sun rays. For this reason, we find that the warmer regions such as Africa or Asia tend to have more brown eyes than the case in European regions. In Iceland, for example, very few people have brown eyes.

And when people move to geographical areas less exposed to the sun, the need for protection given by melanin pigment also decreases, and on this basis we understand that the evolution of our eye color is related to the movement of our ancestors from the colder regions of the globe.

The relationship between eye color and visual diseases

People with brown eyes are less likely to develop tumors, macular degeneration, or diabetic retinopathy. Ophthalmologists believe that the pigment melanin provides great protection for brown eyes.

Why is eye color not a Mendelian trait?

Although eye color is usually modeled as a simple, Mendelian trait, further research and observation has indicated that eye color does not follow the classical paths of inheritance. Eye color phenotypes demonstrate both epistasis and incomplete dominance.

Why is the iris different from person to person?

The pattern of your iris differs in each eye. This even holds true for identical twins. How does that happen? As the developing fetus opens and shuts its eyes in utero, iris tissue tightens and folds randomly, so no two can be the same.

What is it called when you have a different color around your iris?

Rather than have one distinct eye color, people with central heterochromia have a different color near the border of their pupils. A person with this condition may have a shade of gold around the border of their pupil in the center of their iris, with the rest of their iris another color.

What is it called when a person has irises of different colors?

What Is Heterochromia? Heterochromia is when a person's irises are different colors. There are a few kinds of heterochromia. Complete heterochromia is when one iris is a different color than the other. When part of one iris is a different color than the rest of it, this is called partial heterochromia.

What is the difference between polygenic and Mendelian inheritance?

Polygenic inheritance describes the inheritance of traits that are determined by more than one gene. These genes, called polygenes, produce specific traits when they are expressed together. Polygenic inheritance differs from Mendelian inheritance patterns, where traits are determined by a single gene.

Are there Mendelian traits in humans?

Examples of human autosomal Mendelian traits include albinism and Huntington's disease. Examples of human X-linked traits include red-green colour blindness and hemophilia.

What is polygenic vs Mendelian traits?

While Mendelian traits tend to be influenced by a single gene, the vast majority of human phenotypes are polygenic traits. The term polygenic means “many genes.” Therefore, a polygenic trait is influenced by many genes that work together to produce the phenotype.

What is melanin in eyes?

Melanin is a pigment that gives color to your eyes, hair and skin. Genes determine your eye color. The iris (the colored part of the eye) can range from light blue or gray to very dark brown, in a full spectrum of shades. No two people have the exact same color eyes.

Is different eye color a mutation?

What causes heterochromia? The most common cause of heterochromia is a genetic mutation that results in an individual born with two differently colored eyes. This mutation is not usually harmful and, as mentioned, usually does not influence the quality of vision.

What is the evolutionary reason for different eye colors?

One theory is the Vitamin D hypothesis, which is the idea that light colored skin, hair, and eyes co-evolved as humans moved into latitudes with shorter days, shorter summers, and therefore, less sunlight.

Is eye color polygenic or Mendelian?

polygenic trait

Genetic determination of eye color

It was originally thought that eye color was a simple Mendelian trait, meaning it was determined by a single gene, with brown being dominant and blue recessive. It is now clear that eye color is a polygenic trait, meaning it is determined by multiple genes.

Why is the color of the iris not the same on other people or races?

Eye color is determined by variations in a person's genes. Most of the genes associated with eye color are involved in the production, transport, or storage of a pigment called melanin. Eye color is directly related to the amount of melanin in the front layers of the iris.

Does Mendelian genetics apply to eye color?

In the most elementary form, the inheritance of eye color is classified as a Mendelian trait. On the basis of the observation of more than two phenotypes, eye color has a more complex pattern of inheritance. Eye color ranges include varying shades of brown, hazel, green, blue, gray, and in rare cases, violet and red.