Eye color: how it is passed on from parents to child. Calculate the child's eye color.

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Eye color: from grandparents to our grandchildren: how it is transmitted genetically.
Tables for calculating the eye color of an unborn child.

During pregnancy, many parents are eager to find out what eye color their unborn child will have. All answers and tables for calculating eye color are in this article.

Good news for those who want to pass on their exact eye color to their descendants: it is possible.

Recent research in the field of genetics has discovered new data on the genes that are responsible for eye color (previously 2 genes were known that were responsible for eye color, now there are 6). At the same time, today genetics does not have answers to all questions regarding eye color. However, there is a general theory that, even with the latest research, provides a genetic basis for eye color. Let's consider it.

So: every person has at least 2 genes that determine eye color: the HERC2 gene, which is located on human chromosome 15, and the gey gene (also called EYCL 1), which is located on chromosome 19.

Let's look at HERC2 first: humans have two copies of this gene, one from their mother and one from their father. HERC2 can be brown and blue, that is, one person has either 2 brown HERC2 or 2 blue HERC2 or one brown HERC2 and one blue HERC2:

(*In all tables in this article, the dominant gene is written with a capital letter, and the recessive gene is written with a small letter, eye color is written with a small letter).

Where does the owner of two blue ones come from? HERC2 green eye color - explained below. In the meantime, some data from the general theory of genetics: brown HERC2 - dominant, and blue is recessive, so the carrier has one brown and one blue HERC2 eye color will be brown. However, to his children the bearer of one brown and one blue HERC2 with a 50x50 probability it can transmit both brown and blue HERC2 , that is, the dominance of brown has no effect on the transfer of the copy HERC2 children.

For example, a wife has brown eyes, even if they are “hopelessly” brown: that is, she has 2 copies of brown HERC2 : All children born to such a woman will be brown-eyed, even if the man has blue or green eyes, since she will pass on one of her two brown genes to the children. But grandchildren can have eyes of any color:

So, for example:

HERC2 about the mother's t is brown (the mother, for example, has both HERC2 brown)

HERC2 from the father - blue (father, for example, has both HERC2 blue)

HERC2 The child has one brown and one blue. The eye color of such a child is always brown; at the same time your HERC2 he can pass on the blue color to his children (who can also receive it from the second parent HERC2 blue and then have eyes either blue or green).

Now let's move on to the gene gay: it comes in green and blue (blue, grey); each person also has two copies: a person receives one copy from his mother, the second from his father. Green gay is the dominant gene, blue gay - recessive. A person thus has either 2 blue genes gay or 2 green genes gay or one blue and one green gene gay . At the same time, this affects the color of his eyes only if he has HERC2 from both parents - blue (if he received brown from at least one of the parents HERC2 , his eyes will always be brown).

So, if a person received blue from both parents HERC2 , depending on the gene gay his eyes can be the following colors:

gay gene: 2 copies	Human eye color
Green and Green	green
Green and blue	green
blue and blue	blue

General table for calculating a child's eye color, brown eye color is designated "K", green eye color is designated "Z" and blue eye color is designated "G":

HERC2	Gey	eye color
QC	ZZ	brown
QC	Zg	brown
QC	GG	brown
Kg	ZZ	brown
Kg	Zg	brown
Kg	GG	brown
yy	ZZ	green
yy	Zg	green
yy	GG

3) One of the forms of glaucoma is determined by a dominant autosomal gene, and the second has an autosomal recessive type of inheritance. These genes are located on different pairs of chromosomes.
What is the probability of having a sick child if both parents are diheterozygous?

4) The gene for black color in cats is sex-linked. The other allele of this gene corresponds to the red color; heterozygous animals have a spotted ("tortoiseshell") coloration.
What will be the offspring from crossing a “tortoiseshell” cat with a ginger cat?

5) The forensic medical examination is tasked with finding out whether the boy in the family is his own or adopted. A blood test of the husband, wife and child showed: the wife is Rh-AB-IV blood type, the husband is Rh+O (I) blood type, the child is Rh-B (III) blood type.
What conclusion should the expert give and on what is it based?

6) When crossing a brown Great Dane with a white one, all the offspring are white. When breeding the resulting offspring "in themselves" we got 40 white, 11 black and 3 brown.
What type of gene interaction determines the inheritance of coat color in Great Danes? What is the genotype of the parents and offspring?

7) In chickens, striped color is due to the sex-linked dominant (B), and the absence of such striping is due to its recessive alleles (c). The presence of a crest on the head is a dominant autosomal gene (C), and its absence is a recessive allele (c). Two striped, combed birds were crossed and produced two chicks: a striped cockerel with a comb and a non-striped hen without a comb. Indicate the genotypes of the parental forms and offspring.

1) In humans, the gene for curly hair (A) dominates over the gene for smooth hair (a), and the gene for normal hearing (B) dominates over the gene for deaf-muteness (c). In a family where the parents are good

heard; but one has smooth hair and the other has curly hair, a deaf child was born with smooth hair. Their second child heard well and had curly hair.
What is the probability of having a deaf child with curly hair in such a family?

2) The gene for brown eyes is dominant over the gene for blue eyes. A brown-eyed man whose parent had blue eyes married a brown-eyed woman whose father had blue eyes and whose mother had brown eyes.
What kind of offspring can be expected from this marriage?

in humans, the gene for brown eyes dominates in humans, the gene for brown eyes dominates over the gene that determines blue eye color, and the gene that determines the ability to perform better

Right-handedness predominates over the left-handedness gene. What is the probability of having blue-eyed, left-handed children from the marriage of two diheterozygous parents?

in humans, the gene for brown eyes dominates the gene causing blue eyes, a blue-eyed man, one of whose parents has brown eyes, marries

a brown-eyed woman whose father has brown eyes and whose mother has blue eyes. What kind of offspring can be expected from this marriage.

1. A blue-eyed man, whose parents had brown eyes, married a brown-eyed woman, whose father had blue eyes and whose mother had blue eyes.

brown. What kind of offspring can be expected from this marriage if it is known that the gene for brown eyes dominates the gene for blue eyes?
2. There were two brothers in the family. One of them, a patient with hemorrhagic diathesis, married a woman also suffering from this disease. All three of their children (2 girls and 1 boy) were also sick. The second brother was healthy and married a healthy woman. Of their four children, only one was sick with hemorrhagic diathesis. Determine which gene determines hemorrhagic diathesis.
3. In a family where both parents had normal hearing, a deaf child was born. Which trait is dominant? What are the genotypes of all members of this family?
4. A man suffering from albinism marries a healthy woman whose father suffered from albinism. What kind of children can be expected from this marriage, given that albinism is inherited in humans as an autosomal recessive trait?

We do not choose the color of our eyes, the shape of our ears and nose - these and many other features are inherited from our parents and distant ancestors, the existence of which we can only guess. The quality of vision, hearing or smell does not depend on the shape of the organ of perception, but family traits are sometimes something like a certificate of membership in a clan. Some families are famous for their tall stature, while in others the “trick” is protruding ears or club feet. The inheritance of eye color is not one of the strictly transmitted traits, but there are still certain patterns.

Eye color: diversity and genetics

There are 7 billion people living on Earth, each of whom has a set of individual traits. The color of the iris is one of the features that remains virtually unchanged in an adult, although in older people it loses its brightness.

Scientists counted several hundred possible shades and classified them. For example, according to the Bunak scale, the rarest are yellow and blue irises. The Martin Schultz scale classifies black eyes as rare. There are also anomalies: in albinos, with a complete absence of pigment, the iris is white. Interesting research on how the unequal color of two eyes is inherited.

Formation of iris color

The iris consists of two layers. In the anterior, mesodermal layer is the stroma, which contains melanin. The color of the iris depends on the distribution of the pigment. The color of the posterior, ectodermal layer is always black. The exception is albinos, who are completely devoid of pigments.

Basic colors:

Blue and cyan

The iris fibers are loose and contain a minimum of melanin. There is no pigment in the shells; reflected scattered light creates the impression of blue. The thinner the stroma, the brighter the azure. Almost all people are born with heavenly eyes; this is the common eye color for all babies. Genetics in humans manifests itself towards the end of the first year of life.

In blue-eyed people, the whitish collagen fibers in the stroma are more densely distributed. The first blue-eyed people appeared on the planet about 10,000 years ago thanks to a gene mutation.

Blue-eyes inhabit mainly the north of Europe, although they are found throughout the world.

Grey

With a high collagen density in the outer layer of the membrane, the iris is gray or blue-gray. Melanin and other substances can add yellow and brown impurities to the color of the iris.

Many gray-eyed people live in the north and east of Europe.

Green

It appears when yellow or light brown pigment and diffused blue or cyan are mixed. With this coloring, many shades and uneven distribution across the iris are possible.

Pure green is very rare. The best chances to see them are in Europe (Iceland and the Netherlands) and Turkey.

Amber

The yellow-brown iris may have a greenish or copper tint. There are very light and dark varieties.

Olive (walnut, green-brown)

The shade depends on the lighting. Formed by mixing melanin and blue. There are shades of green, yellow, brown. The color of the iris is not as uniform as amber.

Brown

If there is a lot of pigment in the iris, a brown color of varying intensity is formed. People with such eyes belong to all races and nationalities; brown-eyed people make up the majority of humanity.

Black

When the concentration of melanin is high, the iris is black. Very often, the eyeballs of black-eyed people are yellowish or grayish. Representatives of the Mongoloid race are usually black-eyed, even newborns are born with an iris saturated with melanin.

Yellow

A very rare phenomenon, it usually occurs in people suffering from kidney disease.

How is eye color inherited?

The inheritance of eye color in humans is beyond doubt among geneticists.

• Light is formed due to a mutation in the OCA2 gene.
• Blue and green - EYCL1 gene of chromosome 19.
• Brown - EYCL2.
• Blue - EYCL3 chromosome 15.
• And the genes SLC24A4, TYR are also involved in formation.

According to the classical interpretation, the heredity of eye color occurs as follows: “dark” genes dominate, and “light” genes are recessive. But this is a simplified approach - in practice, the probability of inheritance is quite wide. The combination of genes determines eye color, but genetics can present unexpected variations.

Eye color is inherited

Almost all human babies are born with blue eyes. Inheritance of eye color in children appears approximately six months after birth, when the iris acquires a more pronounced color. By the end of the first year, the iris is filled with color, but final formation is completed later. In some children, the eye color determined by genetics is established by the age of three or four, while in others it is formed only by ten.

Inheritance of eye color in humans appears in childhood, but with age the eyes may become pale. In old people, pigments lose their saturation due to degenerative processes in the body. Some diseases also affect eye color.

Genetics is a serious science, but it cannot say with certainty what kind of eyes a person will have.

90% of the probability of eye color is determined by hereditary factors, but 10% should be left to chance. Eye color (genetics) in a person is determined not only by the color of the iris of the parents, but also by the genome of ancestors up to the fifth generation.

Eye color (genetics) in a child

The established idea that eye color is literally inherited is erroneous and outdated. A child of a brown-eyed father and mother may well be blue-eyed if one of the grandparents or more distant ancestors had light eyes.

To understand how eye color is inherited, it should be taken into account that each person inherits the genes of his mother and father. In these pairs - alleles, some genes can dominate over others. If we talk about a child’s inheritance of eye color, the “brown” gene is dominant, but the “set” may consist of recessive genes.

Probability of a child's eye color

It can be predicted with a high degree of certainty that the child will be born blue-eyed, but the iris will change with age. It’s definitely not worth drawing conclusions at birth, since the inheritance of eye color in children does not appear immediately.

For many years, geneticists could not come to a common opinion on how eye color is inherited in children. The most convincing hypothesis was that of the Austrian biologist and botanist Gregor Johann Mendel, who lived in the 19th century. The abbot in his teaching, using the example of inheritance of hair color, suggested that dark genes always dominate light ones. Subsequently, Darwin and Lamarck developed the theory and came to a conclusion about how eye color is inherited.

Schematically, the patterns of inheritance of eye color by children can be described as follows:

• Brown-eyed or black-eyed parents will have dark-eyed children.
• If the parents are light-eyed, the child will inherit their eye color.
• A child born to parents with dark and light eyes will inherit a dark (dominant) or medium iris color.

Science, which grew from these observations and generalizations, calculated the heredity of eye color in children as accurately as possible. Knowing how eye color is inherited, you can fairly accurately determine which eyes your descendant will inherit.

How is eye color inherited in children?

There cannot be one hundred percent certainty in one result, but the child’s likely inheritance of eye color can be predicted quite accurately.

Eye color (genetics) in a child:

1. With two brown-eyed parents, a child inherits their eye color in 75% of cases, the probability of getting green is 18%, and blue is 7%.
2. Green and brown eyes of father and mother determine the inheritance of eye color by the child: brown - 50%, green - 37%, blue - 13%.
3. Blue and brown eyes of mom and dad mean that the child should not have green eyes. The child can be brown-eyed (50%) or blue-eyed (50%).
4. For a green-eyed couple, the likelihood of having a baby with brown eyes is very small (1%). Eyes will be green (75%) or blue (24%).
5. A child born from a union of green-eyed and blue-eyed partners cannot have brown eyes. Eye color (genetics) is equally likely to be green or blue.
6. And also a brown-eyed child cannot be born to blue-eyed parents. With 99% accuracy, he will inherit his parents' eyes and there is a small chance that his iris will be green (1%).

Interesting facts about eye color. Genetics in practice

• Most people on Earth have brown eyes.
• Only 2 percent of people look at the world with green eyes. Most of them are born in Turkey, but in Asia, the East and South America they are a real rarity.
• Many representatives of the peoples of the Caucasus have blue eyes.
• Icelanders are a small nation, but most of them are green-eyed.
• Eyes of different colors are an almost unique phenomenon, but this is not a pathology. Multi-colored eyes always attracted attention.
• Grass-colored eyes are often combined with red hair. Perhaps this explains the uniqueness - the Inquisition considered red-haired and green-eyed girls to be witches and mercilessly exterminated them.
• The iris of albinos is practically devoid of melanin; blood vessels are visible through the transparent membrane, so the eyes become red.
• At birth, a person receives eyes of a ready size. The ears and nose continue to grow slowly throughout life, but the eyeballs remain the same.
• All blue-eyed people share a common ancestor. The genetic mutation that resulted in the appearance of the first blue-eyed man appeared 6 to 10 thousand years ago.

It is difficult to predict exactly what the eyes of an unborn child will be like, because it is not always possible to take into account all hereditary factors. The color of the iris can change until the age of ten - this is within normal limits.

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.

To answer the question The gene for brown eyes is considered dominant. Does he always win if the other parent's eyes are not brown? given by the author old-timer the best answer is 3:1, unless I forgot the arithmetic. That is, such parents will have three children with brown eyes, and the fourth with blue eyes. But if the brown-eyed person himself has grandparents with different eye colors, the likelihood that the child will be blue-eyed increases MAYBE....

Answer from Alina[guru]
No not always. Mom's eyes are brown, father's are blue. I have brown ones, my sister has blue ones, and my second sister has green ones. My son's father has brown eyes, that is, both parents have brown eyes, but his son's eye color is green.

Answer from Neurosis[guru]
no, in my opinion this is nonsense... if he doesn’t always win, why is he dominant?

Answer from Accomplice[newbie]
No, no and NO! My mom and dad are brown-eyed, and I have blue eyes! My husband has brown ones, and our children have blue ones! Here!

Answer from Alexey 11[guru]
Unfortunately it is so

Answer from Larisa Pavlova[guru]
no, not always, my eyes are gray and my husband’s are brown, our daughter’s eyes are gray like mine

Answer from EYES GREEN KNEES BLUE[guru]
In our case, the brown one won))) as you know, I have green eyes))

Answer from Diver[active]
not always but often

Answer from N.[guru]
We went through this at school, there are calculations on the power of probability, open the textbook “General Biology”.)

Answer from Yatyana[guru]
I have brown eyes, my husband has blue eyes, but my daughter still has blue eyes like her husband, which means that brown ones do not always dominate

Answer from Olka[newbie]
Not always!! ! A child does not necessarily inherit a dominant gene, but can also inherit a recessive one if it was present in previous generations). And we have brown-eyed parents and a blue-eyed daughter))

Answer from Anna Zilina[active]
won against us. My husband has brown eyes, my daughter also has brown eyes.

Answer from Kisa[expert]
Biology textbook for 9th grade. No not always.

Answer from ~Give me the Crown, Darling~[guru]
not always. my father is brown, and my mother is green

Answer from MarS[guru]
My wife and I have brown eyes, and my daughter has blue eyes, like her grandfather’s. AND.. . such a paradox. Until I was seven years old, my eyes were blue, and then they suddenly turned brown, that is, they became caried-dominated:.... (my father had blue eyes, my mother had brown eyes).

Answer from Irina I[guru]
Not always.

Answer from Hyperv strat[newbie]
We cannot isolate all alleles. Compared to all common alleles, it wins. But what if there is such a gray-brown-crimson color that its allele is more dominant? It's impossible to say for sure.

Answer from Vita[guru]
not always

Answer from Lyubov Semyonova[guru]
My eyes are green, my husband's are brown, and my daughter's are blue.

Answer from [email protected] [guru]
No. I have brown eyes, but our dad has blue eyes and our daughter has blue eyes.