home Audience 12 Brown eyes are a dominant gene. Child's eye color. Genetic possibility in %. Mechanisms of inheritance of eye color in humans

Brown eyes are a dominant gene. Child's eye color. Genetic possibility in %. Mechanisms of inheritance of eye color in humans

Problem 1. In humans, the gene for brown eyes is dominant over the gene for blue eyes. What is the probability of having blue-eyed children in a family where the mother had blue eyes and the father had brown eyes, and it is known that he is heterozygous for this trait?

Solution: Let's write down the crossing scheme.

R: ♀ aa x ♂ Aa

blue brown

G: (a) (A) , (a)

brown blue

Answer: the probability of having a blue-eyed child is 50%.

Task 2. Phenylketonuria is inherited as an autosomal recessive trait. In a family where both parents were healthy, a child with phenylketonuria was born. What is the probability that the second child in this family will also be sick?

Solution. R: ♀ A- x ♂ A-

Reasoning. Since both parents are healthy, they can have both the AA and Aa genotypes. Since the first child in this family was sick, his genotype is aa. According to the gamete purity hypothesis, the body receives one allele of a gene from the father, and the other from the mother. Consequently, both parents are heterozygous for the analyzed trait - Aa.

Now you can determine the probability of having a second child with a patient:

R: ♀ Aa x ♂ Aa

Norm norm

G: (A), (a) (A), (a)

F 1: AA, 2 Aa, aa

Normal normal phenylketonuria

Thus, 75% of children will be healthy, and 25% will be sick.

Answer: 25%.

Task 3. In some breeds of cattle, polledness is dominant over hornedness.

A) When crossing polled and horned animals, 14 horned and 15 polled offspring were born. Determine the genotypes of the parental forms.

C) As a result of crossing horned and polled animals, all 30 offspring were polled. Determine the genotypes of the parental forms.

C) Crossing polled animals with each other produced 12 polled and 3 horned calves. Determine the genotypes of the parental forms.

Solution. The genotypes of the parents can be determined by segregation in the offspring. In the first case, the splitting was 1:1, therefore there was an analyzing cross:

R: ♀ Aa x ♂ aa

polled horniness

G: (A), (a) (a)

polled hornedness

In the second case, there was uniformity of the offspring, therefore homozygous horned and polled animals were crossed:

R: ♀ AA x ♂ aa

Norm norm

polled

In the third case, a 3:1 split occurred, which is only possible when crossing two heterozygotes:

R: ♀ Aa x ♂ Aa

polled polled

G: (A), (a) (A), (a)

F 1: AA, 2 Aa, aa

polled hornedness

75% - polled

25% - horned

Answer: A) Aa and aa

B) AA and aa

C) Aa and Aa

Task 4. In humans, brown eyes dominate over blue ones, and right-handedness dominates over left-handedness.

1. What is the probability of having a left-handed, blue-eyed child in a family where the mother is blue-eyed and right-handed (although her father was left-handed), and the father has brown eyes and is predominantly left-handed, although his mother was blue-eyed and right-handed?

2. In a family of brown-eyed, right-handed people, a left-handed child with blue eyes was born. What is the probability that your next child will be right-handed and have blue eyes?

♂--вв ♀ааВ-

R: ♀ aaB- x ♂A-bb

Reasoning. First you need to determine the genotypes of the parents. Since the woman’s father was left-handed, she is therefore heterozygous for the B gene; the man is heterozygous for gene A, since his mother had blue eyes.

Examination. Let's write down the crossing scheme:

R: ♀ aaVv x ♂Aavv

Blue, right Car., lion.

G: (аВ), (ав) (Ав), (ав)

F 1: AaBv, aaBv, Aavv, aavv

Kar., right. Goal, right Kar, lion. Blue, lion

Answer: the probability of having a blue-eyed, left-handed child is 25%.

R: ♀ A-B- x ♂ A-B-

Brown-eyed Brown-eyed

Right-handed right-handed

Blue-eyed lefty

Reasoning. Since, according to the gamete purity hypothesis, the organism receives one gene allele from one parent, and the other from the other, then both parents are heterozygous for both pairs of analyzed genes; their genotype is AaBb.

P: ♀ AaBv x ♂ AaBv

Kar. Right Kar. Right

Thus, the probability of having the next right-handed child with blue eyes (genotype aaBb or aaBB) is 3/16 (or 18.75%).

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

Blue and green, their inheritance results in two pairs of genes. The shades of these colors are determined by the individual characteristics of the body to distribute melanin in chromatophores, which are located in the iris. Other genes that are responsible for hair color and skin tone also affect the shade of eye color. For blond people with light skin are typical, and representatives of the Negroid race have dark brown eyes.

The gene that is responsible only for eye color is located on chromosome 15 and is called HERC2, the second gene - EYCL 1 is located on chromosome 19. The first gene carries information regarding brown and blue colors, the second - about green and blue.

The dominant color in the HERC2 allele is brown, the dominant color in the EYCL 1 allele is green, and blue eyes are inherited in the presence of a recessive trait in two genes. In genetics, it is customary to denote a dominant trait with a capital letter of the Latin alphabet, and a recessive trait is a lowercase letter. If there are uppercase and lowercase letters in a gene, the organism is heterozygous for this trait and exhibits a dominant color, and a hidden recessive trait can be inherited by a child. A “suppressed” trait will appear in a baby when an absolute recessive allele is inherited from two parents. That is, parents may well have a blue-eyed child or with.

Using Latin letters, brown eye color, which is determined by the HERC2 gene, can be designated AA or Aa; blue eyes correspond to the set aa. When a trait is inherited, the child receives one letter from each parent. Thus, if dad has a homozygous trait of brown eyes, and mom has blue eyes, then the calculations look like this: AA+aa=Aa, Aa, Aa, Aa, i.e. a child can only achieve the Aa set, which manifests itself according to the dominant, i.e. the eyes will be brown. But if the father is heterozygous and has the Aa set, and the mother is blue-eyed, the formula looks like: Aa+aa=Aa, Aa, aa,aa, i.e. there is a 50% chance that a child with a blue-eyed mother will have the same eyes. For blue-eyed parents, the eye inheritance formula looks like: aa+aa=aa,aa, aa, aa, in this case the baby inherits only the recessive allele aa, i.e. his eye color will be blue.

In the EYCL 1 allele, eye color is inherited in the same way as in the HERC2 gene, but only the letter A indicates green. Nature arranges it in such a way that the existing dominant trait of brown eyes in the HERC2 gene “defeats” the existing green trait in the EYCL 1 gene.

Thus, a child will always inherit brown eye color if one of the parents has a homozygous dominant set of AA in the HERC2 gene. If a parent with brown eyes passes on the recessive gene a to the child, i.e. a sign of blue eyes, then the color of the eyes determines the presence of a green dominant trait in the EYCL 1 gene. In cases where a parent with green eyes does not transmit the dominant trait A, but “gives” the recessive allele a, the child is born with blue eyes.

Since eye color is determined by two genes, its shades are obtained from the presence of undetected characteristics. If a child has the AA genetic set in the HERC2 allele, then the eyes will be dark brown. The presence in the HERC2 gene of the trait of brown eyes of type Aa, and in the EYCL 1 gene of the recessive trait aa, causes light brown eyes. The homozygous trait of green eyes AA at the EYCL 1 locus determines a more saturated color than the heterozygous set Aa.

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.

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%.