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 one.
married a brown-eyed woman whose father had brown eyes and whose mother had blue eyes. What kind of offspring can be expected from this marriage?
In humans, the gene for brown eyes dominates the gene causing blue eyes. A blue-eyed man, one of the parents who had brown eyes, got marriedon a brown-eyed woman whose father had brown eyes and his mother had blue eyes. What kind of offspring can be expected from this marriage?
from crossing a cow and a bull,
heterozygous for coat color?
Problem No. 3. Guinea pigs have frizzy hair
wool is determined by a dominant gene, and
smooth - recessive.
1. Crossing two curled pigs between
produced 39 individuals with shaggy fur and
11 smooth-haired animals. How many among
individuals having a dominant phenotype,
must be homozygous for this
sign?
2. A guinea pig with shaggy fur
crossed with an individual having a smooth
wool, gave birth to 28 frizzy and 26
smooth-haired offspring. Define
genotypes of parents and offspring.
Task No. 4. An offspring was obtained at the fur farm
in 225 minks. Of these, 167 animals have
brown fur and 58 bluish-gray minks
coloring. Determine the genotypes of the original
forms, if it is known that the gene is brown
coloring dominates the gene,
defining bluish-gray color
wool
Problem No. 5. A person has a gene for brown eyes
dominates the gene causing
Blue eyes. Blue-eyed man, alone
of whose parents had brown eyes,
married a brown-eyed woman who
the father had brown eyes, and the mother had blue eyes.
What kind of offspring can be expected from this
marriage?
Problem No. 6. Albinism is inherited in
human as a recessive trait. In family,
where one of the spouses is an albino, and the other has
pigmented hair, have two children.
One child is albino, the other is
dyed hair. What is the probability
birth of the next albino child?
Problems on di- and polyhybrid crossing
Problem No. 8. Cattle have a gene
polledness dominates the horned gene, and
gene for black coat color - above the gene
red color. Both pairs of genes are located
in different pairs of chromosomes.
1. What will the calves turn out to be like if they are crossed?
heterozygous for both pairs
signs of a bull and a cow?
2. What kind of offspring should be expected from
crossing a black polled bull,
heterozygous for both pairs of traits,
with a red horned cow?
Problem No. 9. Dogs have black fur.
dominates the coffee, and the short coat
- over the long one. Both pairs of genes are in
different chromosomes.
1. What percentage of black shorthairs
puppies can be expected from crossing two
individuals heterozygous for both traits?
2. The hunter bought a black dog with a short
wool and wants to be sure that it is not
carries genes for long, coffee-colored hair.
Which partner according to phenotype and genotype do you need?
select for crossing to check
genotype of the purchased dog?
Problem No. 10. A person has a gene for brown eyes
dominates the gene that determines
development of blue eye color, and the gene
conditioning the ability to better master
right hand, dominates the gene,
determining the development of left-handedness. Both
pairs of genes are located in different
chromosomes. What kind of children can they be if
Are their parents heterozygous?
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.
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.
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?
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, marriesa 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?
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%).
In humans, the gene for normal hearing (B) dominates over the gene for deafness and is located in the autosome; the gene for color blindness (color blindness - d) is recessive and linked to the X chromosome. In a family where the mother suffered from deafness but had normal color vision, and the father had normal hearing (homozygous) and was color blind, a color blind girl with normal hearing was born. Make a diagram for solving the problem. Determine the genotypes of the parents, daughters, possible genotypes of the children and the likelihood of the future birth of color-blind children with normal hearing and deaf children in this school.
Answer
B – normal hearing, b – deafness.
The mother is deaf, but has normal color vision bbX D X _ .
Father with normal hearing (homozygous), color blind BBX d Y.
The colorblind girl X d X d received one X d from her father and the second from her mother, therefore the mother is bbX D X d .
| P | bbX D X d | x | BBX d Y | ||
| G | bX D | BX d | |||
| bXd | BY | ||||
| F1 | BbX D X d | BbX D Y | BbX d X d | BbX d Y | |
| girls from normal hearing and vision |
boys from normal hearing and vision |
girls from normal hearing, colorblind |
boys from normal hearing, colorblind |
Daughter BbX d X d . Probability of having colorblind children = 2/4 (50%). All of them will have normal hearing, the probability of being born deaf = 0%.
In humans, the gene for brown eyes dominates over blue eyes (A), and the gene for color blindness is recessive (color blindness - d) and linked to the X chromosome. A brown-eyed woman with normal vision, whose father had blue eyes and suffered from color blindness, marries a blue-eyed man with normal vision. Make a diagram for solving the problem. Determine the genotypes of the parents and possible offspring, the likelihood of having color-blind children with brown eyes and their gender in this family.
Answer
A – brown eyes, and – blue eyes.
X D – normal vision, X d – color blindness.
Brown-eyed woman with normal vision A_X D X _ .
The woman's father is aaX d Y, he could only give his daughter aX d, therefore, the brown-eyed woman is AaX D X d.
The woman's husband is aaX D Y.
P AaX D X d x aaX D Y
The probability of having a colorblind child with brown eyes is 1/8 (12.5%) and it is a boy.
One form of anemia (blood disease) is inherited as an autosomal dominant trait. In homozygotes this disease leads to death, in heterozygotes it manifests itself in a mild form. A woman with normal vision, but a mild form of anemia, gave birth to two sons from a healthy (by blood) color-blind man - the first, suffering from a mild form of anemia and color blindness, and the second, completely healthy. Determine the genotypes of the parents, sick and healthy sons. What is the probability of having the next son without anomalies?
Answer
AA – death, Aa – anemia, aa – normal.
X D – normal vision, X d – color blindness.
A woman with normal vision but mild anemia AaX D X _ .
A healthy blood color-blind man aaX d Y.
The first child is AaX d Y, the second child is aaX D Y.
The first child received Y from his father, therefore, he received X d from his mother, therefore, his mother AaX D X d.
P AaX D X d x aaX d Y
The probability of having the next son without anomalies is 1/8 (12.5%).
Deafness is an autosomal trait; color blindness is a gender-linked trait. In the marriage of healthy parents, a child was born who was deaf and color blind. Make a diagram for solving the problem. Determine the genotypes of the parents and the child, its gender, genotypes and phenotypes of possible offspring, the likelihood of having children with both anomalies. What laws of heredity are manifested in this case? Justify your answer.
Answer
Healthy parents gave birth to a sick child, therefore, deafness and color blindness are recessive traits.
A - normal. hearing, a - deafness
X D - normal. vision, X d - color blindness.
The child has aa, the parents are healthy, therefore they are Aa.
The father is healthy, therefore he is X D Y. If the child were a girl, then she would have received X D from her father and would not be color blind. Consequently, the child is a boy and received the color blindness gene from his mother. The mother is healthy, therefore fire X D X d .
P AaX D X d x AaX D Y
| AX D | AY | aX D | aY | |
| AX D | AAX D X D normal hearing normal vision girl |
AAX D Y normal hearing normal vision boy |
AaX D X D normal hearing normal vision girl |
AaX D Y normal hearing normal vision boy |
| AX d | AAX d X D normal hearing normal vision girl |
AAX d Y normal hearing colorblind boy |
AaX d X D normal hearing normal vision girl |
AaX d Y normal hearing colorblind boy |
| aX D | AaX D X D normal hearing normal vision girl |
AaX D Y normal hearing normal vision boy |
aaX D X D deafness normal vision girl |
aaX D Y deafness normal vision boy |
| aX d | AaX d X D normal hearing normal vision girl |
AaX d Y normal hearing colorblind boy |
aaX d X D deafness normal vision girl |
aaX d Y deafness color blindness boy |
The probability of having a child with two anomalies is 1/16 (6.25%).
In this case, Medel's third law (the law of independent inheritance) appeared.
The shape of the wings in Drosophila is an autosomal gene, the gene for eye color is located on the X chromosome. The male sex is heterogametic in Drosophila. When female fruit flies with normal wings and red eyes were crossed and males with reduced wings and white eyes, all offspring had normal wings and red eyes. The resulting F1 males were crossed with the original parent female. Make a diagram for solving the problem. Determine the genotypes and phenotypes of parents and offspring in two crosses. What laws of heredity appear in two crosses?
Answer
In the first generation, uniform offspring were obtained (Mendel's first law), therefore the parents were homozygotes, F1 were heterozygotes, and heterozygotes showed dominant genes.
A - normal wings, a - reduced wings
B - red eyes, b - white eyes
P AAX B X B x aaX b Y
F1 AaX B X b , AaX B Y
AaX B Y x AAX B X B
| AX B | aX B | AY | aY | |
| AX B | AAX B X B |
AaX B X B |
AAX B Y |
AaX B Y |
All offspring turned out to have normal wings and red eyes. In the second crossing, Mendel's third law (the law of independent inheritance) appeared.
In Drosophila, the heterogametic sex is male. Drosophila females with a gray body, red eyes and males with a black body, white eyes were crossed, all the offspring were uniform in body and eye color. In the second crossing of Drosophila females with a black body, white eyes and males with a gray body, red eyes, the offspring were females with a gray body, red eyes and males with a gray body, white eyes. Draw up crossing schemes, determine the genotypes and phenotypes of the parents, offspring in two crosses and the sex of the offspring in the first cross. Explain why the characteristics split in the second crossing.
Answer
A - gray body, a - black body
X E - red eyes, X E - white eyes
Since in the first crossing all the offspring were uniform, therefore, homozygotes were crossed:
P AA X E X E x aaX e Y
F1 AaX E X e, AaX E Y (all with gray body and red eyes)
Second crossing:
P aa X e X e x AAX E Y
F1 AaX e X E, AaX e Y (females with a gray body and red eyes, males with a gray body and white eyes)
The splitting of characters in the second generation occurred because the eye color trait is linked to the X chromosome, and males receive the X chromosome only from the mother.
In humans, the inheritance of albinism is not sex-linked (A - the presence of melanin in skin cells, and - the absence of melanin in skin cells - albinism), and hemophilia is sex-linked (X H - normal blood clotting, X h - hemophilia). Determine the genotypes of the parents, as well as the possible genotypes, sex and phenotypes of children from the marriage of a dihomozygous woman, normal for both alleles, and an albino man with hemophilia. Make a diagram for solving the problem.
Answer
A is normal, a is albinism.
X H - normal, X h - hemophilia.
Woman ААХ Н Х Н, man ааХ Н Х h.
Wing shape in Drosophila is an autosomal gene; the gene for eye size is located on the X chromosome. The male sex is heterogametic in Drosophila. When two fruit flies with normal wings and normal eyes were crossed, the offspring produced a male with curled wings and small eyes. This male was crossed with the parent. Make a diagram for solving the problem. Determine the genotypes of the parents and the resulting F1 male, and the genotypes and phenotypes of the F2 offspring. What proportion of females from the total number of offspring in the second cross is phenotypically similar to the parent female? Determine their genotypes.
Answer
Since crossing two fruit flies with normal wings resulted in a child with curled wings, therefore A - normal wings, a - curled wings, parents Aa x Aa, child aa.
The gene for eye size is linked to the X chromosome, therefore, a male with small eyes received Y from his father, and the gene for small eyes from his mother, but the mother herself had normal eyes, therefore, she was a heterozygote. X B - normal eyes, X b - small eyes, mother X B X b, father X B Y, child X b Y.
F1 AaX B X b x aaX b Y
Phenotypically similar to the parent female will be F2 AaX B X b, their 1/8 (12.5%) of the total number of offspring.
