home Adviсe Child's eye color. Genetic possibility in %. In humans, the gene for brown eyes dominates over the gene that determines the development of blue eye color, and the gene that determines the ability to better use the right hand Mechanisms of inheritance of eye color in humans

Child's eye color. Genetic possibility in %. In humans, the gene for brown eyes dominates over the gene that determines the development of blue eye color, and the gene that determines the ability to better use the right hand Mechanisms of inheritance of eye color in humans

Many mothers, while expecting a baby, often think about how he will be born, what color eyes and hair he will have, what nose, lips and height he will have. Will he look like his parents or will he inherit the features of one of his relatives? Genetics can provide answers to these questions even before the baby is born.

Based on the laws of genetics, let's look at the algorithms by which a child's appearance is most often formed.

Eye color

If dad has dark brown eyes and mom has blue eyes, then the child is likely to have brown eyes. The gene for brown eyes is dominant (strong), and the gene for blue eyes is recessive (weak). If both parents have brown eyes, then they are unlikely to have a child with green, gray or blue eyes. As time passes, they will begin to darken, gradually turning brown.

But if both parents are blue-eyed, then the baby will most likely have blue eyes.

Dominant traits

If at least one parent has dimples on the cheeks, a hooked (or large/crooked) nose, or protruding ears, then there is a very high probability that the child will also have this appearance feature. The fact is that these, as we generally believe, shortcomings are dominant signs and “peck out” in the baby’s appearance.

But, as a rule, only one such feature appears, less often - two at once.

Hair color

The gene for dark hair outweighs the gene for light hair because its pigment is strong. If both parents are fair, then the baby will also be born blonde or light brown. And if dad is a bright brunette, and mom is blonde, then the baby’s hair will be dark or light brown.

Interesting fact: a child who was born dark from this combination may have light-colored children in the future. The fact is that children of mixed genes receive both a strong gene from their father and a weak gene from their mother. Later, the weak gene can “merge” with the weak gene of the partner - and the child’s appearance will be light.

Also, the child may be completely different from you if he inherits wandering genes from distant relatives. Thus, in a brown-haired family, a red-haired baby may suddenly be born, and there are also cases when a dark-skinned child was born to white-skinned parents, even if there were mulattoes in the family even several generations ago.

Source: instagram @sarahdriscollphoto

Curly or smooth hair

Wavy and curly hair is also a dominant trait that is most likely to appear in a child if at least one of the parents has it.

A question that many parents ask. However, it is impossible to answer this question unequivocally, since the answer depends 90% on genetic predisposition and 10% on chance.

Only one thing is clear here - the baby will be born with cloudy gray-blue or dark brown eyes.

What color will my child's eyes be?

Almost always, the eyes of newborns have a blue color, which subsequently, starting from 6 months, begins to change and darken as it is exposed to sunlight (although in most children this occurs between the ages of 6 months and a year). Around the age of three or four, the child’s eyes acquire their permanent color that remains for life.

Predicting a child's eye color

Below is a diagram that shows the “chances of success” of a particular eye color (in % ratio) depending on the eye color of the parents.

Also look at the site - determining the color of a child’s eyes by the color of the eyes of the baby’s parents and the color of the eyes of your parents. This is an English-language resource, but it won’t be difficult to figure out what’s what.

How reliable is this? Let's check it together! Please let us know in the comments whether the eye color in reality coincided with the predictions calculated and proposed using these methods.

Inheritance of eye color from a genetic point of view

The color of a child's eyes is determined by the parents' genes, but great-grandparents also contribute to the child's appearance. It turns out that their colors and shades have a polygenic inheritance pattern and are determined by the number and types of pigments in the iris cornea of the eye.

In general, the color of a person’s eyes depends on the amount of melanin in the iris (melanin is also responsible for the color of our skin). In the spectrum of all possible variety of colors, one extreme point will be blue eye color (the amount of melanin is minimal), and the other is brown (the maximum amount of melanin). People with different eye colors fall somewhere between these extremes. And the gradation depends on the genetically determined amount of melanin in the iris.

Genetic studies show that the pigment component of the iris is controlled by 6 different genes. They interact with each other according to certain clear patterns, which ultimately leads to a wide variety of eye colors.

There is an established opinion that the color of a child’s eyes is inherited according to Mendel’s laws - eye color is inherited in almost the same way as hair color: genes for dark color are dominant, i.e. the distinctive features (phenotypes) encoded by them take precedence over the distinctive features encoded by the lighter color gene.

Parents with dark hair are more likely to have children with dark hair; the offspring of blond parents will be blond; and a child of parents whose hair color is different will have hair whose color will be somewhere in between the parents'.

However, the idea that brown-eyed parents can only have brown-eyed children is a fairly common misconception. A brown-eyed couple may well have a blue-eyed child, especially if one of the close relatives has a different eye color). The fact is that a person copies two versions of one gene: one from the mother, the other from the father. These two versions of the same gene are called alleles, with some alleles in each pair being dominant over the others. When it comes to genes that control eye color, brown will be dominant, however, a child can also receive a recessive allele from either parent.

Let us note some patterns in the inheritance of eye color by a child:

Your husband and you have blue eyes - 99%, that the child will have exactly the same color or light gray. Only 1% gives the chance that your baby will have green eyes.
If one of you has blue eyes and the other has green eyes, then the chances of the child having both eye colors are equal.
If both parents have green eyes, then there is a 75% chance that the baby will have green eyes, a 24% chance of blue eyes, and a 1% chance of brown eyes.
The combination of blue and brown eyes in parents gives a 50% to 50% chance for the child to have one or the other eye color.
Brown and green parental eyes are 50% of children's brown eyes, 37.5% of green eyes and 12.5% of blue eyes.
Both parents have brown eyes. This combination will give the baby the same color in 75% of cases, green in 19%, and only in 6% babies can be blue-eyed.

Some fun facts about eye color

The most common eye color around the world is brown.
The rarest eye color is green - less than 2% of the total population of the Earth.
Turkey has the highest percentage of citizens with green eyes, namely: 20%.
For residents of the Caucasus, blue eye color is the most characteristic, not counting amber, brown, gray and green. Also, more than 80% of Icelandic residents have either blue or green eye color.
There is such a phenomenon as heterochromia (from the Greek ἕτερος - “different”, “different”, χρῶμα - color) - different color of the iris of the right and left eyes or unequal coloring of different parts of the iris of one eyes.

Now you know what color your child’s eyes will be, and we, in turn, wish that, regardless of the color, there is only happiness and joy in his beloved eyes!

What happens to a child who is heterozygous for eye color? The answer is: he will have brown eyes.

The fact is that the child has one gene that can form a large amount of tyrosinase, and a gene that can form a small amount of tyrosinase. However, a single gene can produce a relatively large amount of tyrosinase, and this may be enough to turn the eyes brown.

As a result, two parents, one of whom is homozygous for brown eyes and the other homozygous for blue eyes, have children who are heterozygous and at the same time have brown eyes. The gene for blue eyes does not appear.

When a person has two different genes for some physical characteristic at identical locations on a pair of chromosomes and only one gene is expressed, that gene is called dominant. A gene that is not expressed is recessive. In the case of eye color, the gene for brown eyes is dominant to the gene for blue eyes. The gene for blue eyes is recessive to the gene for brown eyes.

It is impossible to tell just by looking at a person whether he is homozygous or heterozygous for brown eyes. Either way, his eyes are brown. One way to say something definitive is to find out something about his parents. If his mother or his father had blue eyes, he must be heterozygous. Another way to know something is to see the color of his children's eyes.

We already know that if a man who is homozygous but has brown eyes marries a woman who is homozygous for brown eyes, they will have children who are homozygous for brown eyes. But what will happen if he marries a heterozygous girl? A homozygous male would only form sperm cells with brown eye genes. His heterozygous wife would produce two types of eggs. During meiosis. since her cells have both a brown eye gene and a blue eye gene, the brown eye gene will travel to one end of the cell and the blue eye gene to the other. Half of the formed eggs will contain the gene for brown eyes, and the other half will contain the gene for blue eyes.

You need to understand that eye color depends not only on the pigment produced. The iris consists of anterior and posterior layers. The color of the eye depends on the distribution of pigments in different layers. In addition, the vessels and fibers of the iris play a role. For example, green eye color is determined by the blue or gray color of the back layer of the iris, and light brown pigment is distributed in the front layer. The total is green.

The definition of gray and blue eyes is similar, only the density of the fibers of the outer layer is even higher and their shade is closer to gray. If the density is not so high, then the color will be gray-blue. The presence of melanin or other substances produces a small yellow or brownish impurity.

The structure of the black iris is similar to the brown one, but the concentration of melanin in it is so high that the light incident on it is almost completely absorbed.

The chance of a sperm cell fertilizing an egg with the gene for brown eyes or an egg with the gene for blue eyes is therefore 50/50. Half of the fertilized eggs will be homozygous for brown eyes, and half will be heterozygous. But all children will have brown eyes.

Now suppose that both father and mother are heterozygous. Both would have brown eyes, but both would also have the gene for blue eyes. The father would form two kinds of sperm cells, one with the gene for blue eyes and one with the gene for brown eyes. In the same way, the mother would form two types of eggs.

Several combinations of sperm and egg cells are now possible. Suppose one of the sperm cells with the brown eye gene fertilizes one of the eggs with the brown eye gene. The child in this case will be homozygous for brown eyes and will naturally have brown eyes. Suppose that a sperm cell with a gene for brown eyes fertilizes an egg cell with a gene for blue eyes, or a sperm cell with a gene for blue eyes fertilizes an egg cell with a gene for brown eyes. In either case, the child will be heterozygous and will still have brown eyes.

But there is another option. What if a sperm cell with the blue eye gene fertilizes an egg with the blue eye gene?

In this case, the child will be homozygous for blue eyes and will have blue eyes.

Thus, two brown-eyed parents can have a blue-eyed child. A gene that had seemed to disappear appeared again.

Besides, you can tell something about the parents by looking at the child. Although their eyes are brown, just like the homozygous person, you know that they both must be heterozygous, otherwise the gene for blue eyes would not express itself.

Chapter from the book " Races and peoples»

William Boyd "Tsentrpoligraf" 2005

Approximate map of the distribution of blue and green eyes in Europe.

Blue And blue eyes are most common among the European population, especially in the Baltics and Northern Europe. Eyes of these shades are also found in the Middle East, for example, in Afghanistan, Lebanon, Iran.

Grey eye color is most common in Eastern and Northern Europe. It is also found in Iran, Afghanistan, Pakistan and parts of Northwest Africa.

Purely green eye color is extremely rare. Its speakers are found in Northern and Central Europe, less often in Southern Europe.

Brown- the most common eye color in the world. It is widespread in Asia, Oceania, Africa, South America and Southern Europe.

Black the type is widespread primarily among the Mongoloid race, in South, Southeast and East Asia.

PSYCHOLOGY

Psychology of sympathy

Appearance is not the only factor on which our attitude towards people depends. When we get to know a person, in addition to his appearance, we immediately notice his other properties that enhance or, conversely, reduce the impression that his appearance made on us.

There are certain prevailing ideas about what a positive person should be. So, many of us are convinced that a girl should be beautiful and a man should be smart. If you look at it, the requirement is quite cruel: clearly, not all girls are beautiful, just as not all men are very smart (after all, when we say “smart,” we mean that he is smarter than others, smarter than the majority, stands out from the majority). It turns out that we are ready to recognize only some privileged part of our fellow citizens as worthy of attention, defining everyone else an order of magnitude lower. In everyday life, of course, we don’t think about it, we don’t analyze this stereotype so deeply, but it lingers in our consciousness, takes root, and it turns out that it’s not always easy to get rid of it.

The next circumstance on which the emergence of sympathy depends is the dissimilarity or similarity of the partners. They often say that these people got together because they are similar to each other. They say it no less often. that people got together precisely because they were very different. Depending on the situation, either one or the other is significant.

Incredible facts

Researchers have proven that Blue eye color is the result of a genetic mutation that probably occurred between 6,000 and 10,000 years ago. Scientists say they have discovered the reason why some of us have blue pigment in the iris.

Professor Hans Eiberg, leader of the research team at the University of Copenhagen, claims that all humans originally had brown eyes. As a result of a genetic mutation, the color of the eyes has changed, and both of these pigments are present in the iris of the eyes of modern people.

According to experts, most likely blue eye color comes from the countries of the Middle East or the northern part of the Black Sea coast. It was in this area that the largest migration took place during the Neolithic period (about 6,000 - 10,000 years ago). People moved in huge groups to the northern part of Europe.

"These are just our guesses," says Professor Eyberg. According to him, this could also be the territory of the northern part of Afghanistan.

Genetic mutation

This mutation, which occurred thousands of years ago, affected the so-called OCA2 gene and literally, “turned off” the ability of brown eyes to produce dark pigment.

For those less educated on this issue, it is worth explaining that the OCA2 gene is involved in the production of melanin, the pigment that gives color to hair, eyes and skin. A mutation in neighboring genes does not completely immobilize the OCA2 gene, but it certainly limits its action, thereby reducing the production of melanin in the iris. Thus, brown eyes are “diluted” with blue pigment.

If the OCA2 gene were completely turned off, those who inherited this mutation would lose melanin for their skin, hair and iris. Sometimes this happens. We call people with a complete lack of melanin albinos.

Professor Eyberg and his colleagues examined the DNA of blue-eyed people from countries where the majority of the population has brown eyes. Residents of Jordan, India, Denmark and Turkey took part in a number of experimental observations.

The results of Professor Eyberg's research are very important for genetics in general. For the first time in 1996, a scientist suggested that the OCA2 gene is responsible for eye and hair color. From this moment, a very important stage began in the study of the OCA2 gene, as well as all processes in the body associated with this gene.

The results of this study were published in the journal Human Genetics, which clearly indicate that all blue-eyed inhabitants of our planet were once the owners of brown eyes, and only as a result of the mutation that occurred, the pigment of the eyes changed.

Albinism in humans

It is known that the cause of albinism is the absence of the enzyme tyrosinase, which is involved in the normal synthesis of melanin.

There are several main types of this genetic disorder:

1. Oculocutaneous albinism.

2. Temperature-sensitive albinism.

3. Ocular albinism.

Treatment of any of these types is unsuccessful. It is impossible to compensate for the lack of melanin or prevent various visual disorders that are an integral part of the disease.

Question: In humans, the gene for brown eyes dominates over blue eyes, and the ability to use predominantly the right hand dominates over left-handedness. The genes are not linked. A blue-eyed, right-handed man married a brown-eyed, right-handed woman. They had two children: a brown-eyed left-hander and a blue-eyed right-hander. Determine the probability of birth in this family of blue-eyed children who control predominantly the left hand.

In humans, the gene for brown eyes dominates over blue eyes, and the ability to use predominantly the right hand dominates over left-handedness. The genes are not linked. A blue-eyed, right-handed man married a brown-eyed, right-handed woman. They had two children: a brown-eyed left-hander and a blue-eyed right-hander. Determine the probability of birth in this family of blue-eyed children who control predominantly the left hand.

Answers:

Phenotype gene genotype brown A AA, Aa blue a aa right-handed B BB, BB left-handed in BB solution P mother AaBv*father aaBv G AB, Av, aB, av, aB, av F1 AaBB, AaBv, aaBB, aaBv, AaBv, Aavv ,ааВв,аавв kar kar gol kar kar gol gol pr pr pr pr pr right left right left Answer: the probability of giving birth to a blue-eyed left-hander is 1/8 or 12.5%

Given: A --- brown eyes AA, Aa a --- blue eyes aa B --- right-handedness BB, Bb b --- left-handedness bb Find: the probability of the birth in this family of blue-eyed children who control predominantly their left hand --- ? Solution: P: ♀AaBb x ♂aaBb G: AB aB Ab ab aB ab F₁: AaBB --- brown eyes; right-handedness; AaBb --- brown eyes; right-handedness; aaBB --- blue eyes; right-handedness; aaBb --- blue eyes; right-handedness; AaBb --- brown eyes; right-handedness; Aabb --- brown eyes; left-handedness; aaBb --- blue eyes; right-handedness; aabb --- blue eyes; left-handedness; ----1/8*100%=12.5% Answer: the probability of birth in this family of blue-eyed children who control predominantly the left hand is ---12.5%.