1. What is characteristic of a pedigree with an X-linked dominant type of inheritance?
- only women get sick
- both men and women are affected, but there are 2 times more sick women than men.
2. What is characteristic of a pedigree in an autosomal recessive type of inheritance?
- predominantly men are affected
- trait occurs in a generation
- only women get sick
3. What is typical for a pedigree with a Y-linked type of inheritance?
- trait occurs in a generation
- occurs only in women
- the trait is equally likely to occur in both sexes
- the trait occurs only in males
4. What is characteristic of a pedigree with an autosomal dominant type of inheritance?
- trait occurs in a generation
- trait occurs in every generation
- predominantly men are affected
- only women get sick
5. What splitting in the offspring will be observed when crossing Aa x aa:
- uniformity of descendants
6. What splitting in the offspring will be observed when crossing Aa x Aa:
- uniformity of descendants
7. The ratio of splitting 1:2:1 by phenotype and genotype in the second generation is possible with
Linkage of genes
conjugation and crossing over
incomplete dominance
joint inheritance of traits
8. How many types of gametes does an organism form with the AABvSSDd genotype?
- four,
- six,
- eight
9. What is the probability of having a blue-eyed (a) fair-haired (c) child from a blue-eyed, dark-haired (B) father and a brown-eyed (A) fair-haired mother, if the parents are heterozygous for one of the signs?
- 12,5%,
10. Paired genes of homologous chromosomes are called
linked
recessive
dominant
allelic
11. The number of gene linkage groups in organisms depends on the number
Pairs of homologous chromosomes
allelic genes
dominant genes
DNA molecules in the cell nucleus
12. What law is implemented in the inheritance of traits when crossing organisms with genotypes: Aa x Aa?
uniformity
splitting
Linked inheritance
independent inheritance
13. What genes show their effect in the first hybrid generation?
allelic
recessive
dominant
linked
14. When crossing dominant and recessive parental individuals, the first hybrid generation is uniform. What explains this?
All individuals have a homozygous genotype
All individuals have the same set of chromosomes
All individuals live in the same conditions
All individuals have a heterozygous genotype
15. Albinism is determined by a recessive autosomal gene, and hemophilia is determined by a sex-linked recessive gene. Specify the genotype of an albino and hemophilic woman.
AaX H Y or AAX H Y
AaX H X H or AA X H X H
ааХ h Х h
16. Eye color in humans is determined by an autosomal gene, color blindness is a recessive gene linked to sex. Specify the genotype of a brown-eyed woman with normal color vision, whose father is color-blind with blue eyes (brown-eyedness dominates over blue-eyedness).
- AAX D X D
- AaX d X d 4)
- aaX D X d
- AaX D X d
17. What ratio of traits by phenotype is observed in the offspring during analyzing crosses, if the genotype of one of the parents is AaBb (the traits are inherited independently of each other)?
- 1:2:1,
- 1:1:1:1,
- 9:3:3:1,
18. When crossing tomatoes with red and yellow fruits, offspring were obtained in which half of the fruits were red and half yellow. What are the genotypes of the parents?
- Aa x AA
- AA x AA
- Aa x aa
- AA x aa
19. The property of organisms to acquire new features, as well as differences between individuals within a species, is a manifestation
- heredity
- struggle for existence
- individual development
- variability
20. Monogenic inheritance is inheritance:
- mitochondrial gene
- pairs of allelic genes
- genes on one chromosome
- a gene in an autosome
21. Autosomal inheritance is characterized by:
- inheritance of genes on the same chromosome
- inheritance of a gene located on the Y chromosome
- inheritance of allelic genes of the X chromosome
- inheritance of genes on homologous chromosomes
22. Sex-linked inheritance is inheritance:
- genes located on the sex chromosomes
- primary sexual characteristics
- signs that determine the sex of the body
- genes responsible for sex formation
23. An organism is called a homogametic sex:
24. I call an organism heterogametic sex:
- its gametes carry the same sex chromosomes
- forming the same gametes according to the composition of alleles
- producing gametes with different alleles
- its gametes carry different sex chromosomes
25. In humans, X-linked is inherited:
- eye color
- albinism
- color blindness
- skin color
26. In humans, X-linked is inherited:
- eye color
- albinism
- hemophilia
- skin color
27. The phenomenon of hemizygosity is normally observed with:
- when there is one allele of a gene in the gene pool
- in the presence of one allele of the gene in the gamete
- in the presence of one allele of the gene in the genotype
- when there is one allele of a gene in the genome
28. Crossover frequency depends on:
- from the distance between genes
- gene interactions
- from gene dominance
- from gene codominance
29. Different variants one gene are called:
- genomes
- alleles
- codons
- anticodons
30. According to the law of “purity of gametes”, a gamete gets:
- one pair of genes
- one pair of homologous chromosomes
- one gene from each allele pair
- one pair of alleles
31. Analyzing cross is carried out for:
- determining the genotype of an individual with a dominant trait
- to determine the type of trait inheritance
- to study mutational processes in a population
- to study the frequency of mutations in the gametes of the body
32. When carrying out monohybrid analyzing crossing, organisms are used:
- heterozygous for many traits
- heterozygous for multiple pairs of alleles
- homozygous for all gene alleles
- homozygous for one pair of alleles
33. Polygenic inheritance is inheritance:
- pleiotropic genes
- alleles for one trait
- more than two genes for the same trait
- codominant genes
34. Independent inheritance characterizes:
- Mendel's first law
- Mendel's second law
- Mendel's third law
- law of "purity of gametes"
35. With independent inheritance, a diheterozygous organism forms:
- one type of gamete
- two types of gametes
- four types of gametes
- eight types of gametes
36. With independent inheritance, a homozygous organism forms:
- one type of gamete
- two types of gametes
- four types of gametes
- eight types of gametes
37. Linked inheritance is characterized by the transfer to descendants:
- all signs of parents
- two or more signs
- all genes in the genome
- two or more genes on the same chromosome
38. Linked inheritance is characterized by inheritance:
- polymeric genes
- genes located on the same chromosome
- complementary genes
- genes for one trait
39. With full linked inheritance, a diheterozygous organism forms:
- one type of gamete
- two types of gametes
- four types of gametes
- eight types of gametes
40. In case of incomplete linked inheritance, a diheterozygous organism forms:
- one type of gamete
- two types of gametes
- four types of gametes
- eight types of gametes
41. How many types of gametes and in what ratio does a diheterozygous organism form with incomplete linked inheritance:
- two types in equal proportion
- two types in different ratio
42. How many types of gametes and in what ratio does a diheterozygous organism form with full linked inheritance:
- two types in different ratio
- two types in equal proportion
- four types in equal proportion
- four types in different proportions
43. Morganide - a unit of measurement of the distance between:
- allelic genes
- genes in different linkage groups
- between interacting genes
- genes in the same linkage group
44. A linkage group is called genes located:
- on one arm of the chromosome
- on one chromosome
- in the genome
- in the genotype
Scientists believe that intellectual abilities are 50–70% determined by genes, and the choice of profession is 40%. At 34%, we have a tendency to be polite and rude. Even the desire to sit in front of the TV for a long time is 45% a genetic predisposition. The rest, according to experts, is determined by upbringing, social environment and sudden blows of fate - for example, diseases.
A gene, just like an individual organism, is subject to action natural selection. If, for example, it allows a person to survive under more severe climatic conditions or longer to withstand physical activity - it will spread. If, on the contrary, it provides the appearance of some harmful trait, then the prevalence of such a gene in the population will fall.
During the fetal development of a child, this influence of natural selection on individual genes can manifest itself in a rather strange way. For example, genes inherited from the father are "interested" in the rapid growth of the fetus - since the paternal organism obviously does not lose from this, and the child grows faster. Maternal genes, on the other hand, promote slower development—which ends up taking longer, but leaving the mother with more energy.
Prader-Willi syndrome is an example of what happens when mom's genes "win". During pregnancy, the fetus is inactive; after birth, the child has a developmental delay, a tendency to obesity, short stature, drowsiness and impaired coordination of movements. It may seem strange that these apparently unfavorable traits are encoded by maternal genes - but it must be remembered that normally the same genes compete with paternal ones.
In turn, the “victory” of paternal genes leads to the development of another disease: Angelman syndrome. In this case, the child develops hyperactivity, often epilepsy and delayed speech development. Sometimes lexicon the patient is limited to just a few words, and even in this case, the child understands most of what is said to him - it is the ability to express his thoughts that suffers.
Of course, it is impossible to predict the appearance of the child. But you can say with a certain degree of certainty what the main features will be. Dominant (strong) and recessive (weak) genes will help us with this.
For each of its external and internal characteristics, the child receives two genes. These genes may be the same (tall, full lips) or different (tall and short, plump and thin). If the genes match, there will be no conflict, and the child inherits full lips and tall stature. Otherwise, the strongest gene wins.
A strong gene is called dominant, and a weak gene is called recessive. Strong genes in humans include dark and curly hair; baldness in men; brown, or green eyes; normally pigmented skin. Recessive traits include blue eyes, straight, blond or red hair, and lack of skin pigment.
When a strong and a weak gene meet, the strong one usually wins. For example, mom is brown-eyed brunette, and dad is blond with blue eyes, with a high degree of probability we can say that the baby will be born with dark hair and brown eyes.
True, brown-eyed parents may have a newborn with blue eyes. Thus, the genes received from the grandmother or the grandfather could affect. The opposite situation is also possible. The explanation is that it turns out that not one gene from each parent, as was previously believed, is responsible for any trait, but a whole group of genes. And sometimes one gene is responsible for several functions at once. So a number of genes are responsible for the color of the eyes, which each time are combined in a different way.
Hereditary diseases transmitted by genes
A baby can inherit from his parents not only appearance and character traits, but also diseases (cardiovascular, oncological, diabetes, Alzheimer's and Parkinson's).
The disease may not manifest itself if elementary safety measures are taken. Tell the gynecologist in detail about serious health problems not only for you and your husband, but also for close relatives. This will help protect the baby in the future. Sometimes completely healthy parents give birth to a baby with a hereditary disease. It was laid down in the genes and manifested itself only in the child. This usually happens when both parents have the same disease in their genes. Therefore, if a child is planned, according to experts, it is better to undergo a genetic examination. This is especially true of a family in which children with hereditary diseases were already born.
A weak gene may not be detected in one or many generations until two recessive genes from each parent meet. And then, for example, such a rare sign as albinism may appear.
Chromosomes are also responsible for the sex of the child. For a woman, the chances of giving birth to a girl or a boy are equal. The sex of the child depends only on the father. If an egg meets a sperm with an X sex chromosome, it will be a girl. If U - a boy will be born.
What else can depend on genes:
Gender - 100%;
Height - 80% (for men) and 70% (for women);
Blood pressure - 45%;
Snoring - 42%;
Female infidelity - 41%;
Spirituality - 40%;
Religiosity - 10%.
There are also genes responsible for the development of certain conditions, such as depression or a tendency to uncontrolled eating.
The level of mutations in men is 2 times higher than in women. Thus, it turns out that humanity owes its progress to men.
All representatives of the human race are 99.9% identical in DNA, which completely sweeps aside any basis for racism.
Pleiotropy - multiple gene action (one gene controls the development of several traits).
Often there is a phenomenon when one pair of genes affects several traits at once. Even Mendel in his experiments established that pea plants with purple flowers, in addition, always have red spots in the axils of the leaves and form seeds covered with a gray or brown peel, and that all these signs depend on the action of one hereditary factor.
When studying the genetic characteristics of Persian wheat N.I.Vavilov established that the dominant black color gene always simultaneously causes strong pubescence of the scales.
In the fruit fly Drosophila, a gene that determines the absence of pigment in the eyes reduces fertility, affects the color of some internal organs, and reduces life expectancy.
In karakul sheep, one gene determines the color of the wool and the development of the scar.
The pleiotropic effect of a gene can be primary or secondary (Fig. 56).
At primary pleiotropy the gene exhibits its multiple effect. For example, in Hartnup's disease, a gene mutation leads to impaired absorption of the amino acid tryptophan in the intestine and its reabsorption in the renal tubules. In this case, the membranes of the epithelial cells of the intestine and renal tubules are simultaneously affected with disorders of the digestive and excretory systems.
In humans, a dominant gene is known that determines the trait "spider fingers" ( Marfan syndrome). At the same time, abnormal development of the fingers is accompanied by a violation of the structure of the lens and the development of heart disease (Fig. 57). Here, the multiple effect is also based on the action of one gene, which causes a violation of the development of connective tissue.
At secondary pleiotropy there is one primary phenotypic trait - the manifestation of a mutant gene, followed by a stepwise process of secondary changes leading to multiple effects. So, with sickle cell anemia, homozygotes have several pathological signs: anemia, an enlarged spleen, damage to the skin, heart, kidneys and brain. Therefore, homozygotes with the sickle cell anemia gene die, as a rule, in childhood. All these phenotypic manifestations of a gene constitute a hierarchy of secondary manifestations. The root cause, the immediate phenotypic manifestation of the defective gene, is abnormal hemoglobin and crescent-shaped red blood cells. As a result, other pathological processes occur sequentially: aggregation and destruction of red blood cells, anemia, defects in the kidneys, heart, brain - these pathological signs are secondary.
In pleiotropy, a gene, acting on one main trait, can also change, modify the manifestation of other genes, in connection with which the concept of modifier genes was introduced. The latter enhance or weaken the development of traits encoded by the "main" gene.
The modifying action of a gene - a gene enhances or weakens the effect of a non-allelic gene. There are "basic action" genes, ie. those that determine the development of a trait or property, such as pigment production, fruit shape, susceptibility or resistance to disease, etc. Along with such genes, apparently, there are genes that by themselves do not determine any qualitative reaction or trait, they only enhance or weaken the manifestation of the action of the "main" gene, i.e. modify it, such genes are called modifiers. Any interacting genes at the same time are the genes of the "main" action on one trait, and on the other (or others) are modifier genes.
Indicators of the dependence of the functioning of hereditary inclinations on the characteristics of the genotype are penetrance And expressiveness.
Considering the action of genes, their alleles, it is necessary to take into account the modifying influence of the environment in which the organism develops. If primrose plants are crossed at a temperature of 15-20 ° C, then in F 1 according to the Mendelian scheme, all generations will have pink flowers. But when such a cross is carried out at a temperature of 35 ° C, then all hybrids will have white flowers. If crossbreeding is carried out at a temperature of about 30 ° C, then different ratio(from 3:1 to 100%) plants with white flowers.
Such a fluctuation of classes during splitting, depending on environmental conditions, is called penetrance - strength of phenotypic expression. So, penetrance - this is the frequency of manifestation of a gene, the phenomenon of the appearance or absence of a trait in organisms that are identical in genotype.
Penetrance varies considerably among both dominant and recessive genes. Along with genes, the phenotype of which appears only under a combination of certain conditions and rather rare external conditions (high penetrance), a person has genes, the phenotypic manifestation of which occurs under any combination of external conditions (low penetrance). Penetrance is measured by the percentage (%) of organisms with a phenotypic trait out of the total number of examined carriers of the corresponding alleles.
If the gene is complete, regardless of environment, determines the phenotypic manifestation, then it has a penetrance of 100% ( full penetrance). However, some dominant genes show up less regularly. So, polydactyly has a clear vertical inheritance, but there are gaps in generations. The dominant anomaly - premature puberty - is inherent only in men, but sometimes the disease can be transmitted from a person who did not suffer from this pathology. Penetrance indicates what percentage of the carriers of the gene is the corresponding phenotype. So, penetrance depends on the genes, on the environment, on both. Thus, this is not a constant property of a gene, but a function of genes under specific environmental conditions.
expressiveness (lat. “expressio” - expression) is a change in the quantitative manifestation of a trait in different individuals-carriers of the corresponding allele.
In dominant hereditary diseases, expressivity may fluctuate. In the same family, hereditary diseases can manifest from mild, barely noticeable to severe: various forms of hypertension, schizophrenia, diabetes mellitus, etc. recessive hereditary diseases within the family, they are manifested in the same way and have slight fluctuations in expressivity.
Thus, penetrance - is the probability of phenotypic manifestation of the gene, which is expressed as a percentage (the ratio of diseased individuals to the number of carriers of the corresponding gene).
expressiveness - the degree of clinical manifestation of the gene, which can be weak or strong. Penetrance and expressivity of genes depend on endogenous and exogenous factors. For example, if a violation in the genome is of decisive importance for the manifestation of hemophilia, then the occurrence of diabetes mellitus depends on the interaction of genetic factors and the external environment. In the latter case, they speak of a hereditary predisposition. The ability of the genotype to manifest itself differently in different environmental conditions is called the reaction norm. The reaction rate is inherited, but changes within the reaction rate are not inherited.
A number of signs similar in external manifestation, including hereditary diseases, can be caused by various non-allelic genes. Such a phenomenon is called genocopy . The biological nature of genocopies lies in the fact that the synthesis of the same substances in the cell in some cases is achieved in different ways.
One of the first to study this phenomenon N.V. Timofeev-Resovsky. At the suggestion of N.V. Timofeev-Resovsky, from the mid-1930s heterogeneous groups began to name groups of genes that give a very similar external manifestation, but are localized in different chromosomes or different loci, such as the group of minute genes that cause the reduction of bristles in Drosophila. This phenomenon is widespread in wildlife, including humans. True, in the genetic literature, it is usually not the term N.V. that is used to designate it. Timofeev-Resovsky "heterogeneous groups", and later (mid-40s of the XX century), proposed by a German geneticist X.Nachtsheim- "genocopies", in addition to which the term "phenocopies" was later introduced.
Phenocopies - modification changes - also play an important role in human hereditary pathology. They are due to the fact that in the process of development, under the influence of external factors, a trait that depends on a particular genotype may change; at the same time, traits characteristic of another genotype are copied. Thus, phenocopy - a non-hereditary change in the phenotype of an organism, caused by the action of certain environmental conditions and copying the manifestation of any known hereditary change - mutation - in this organism.
Various environmental factors, such as climatic, physical, chemical, biological, and social, can play a role in the development of phenocopies. Congenital infections (rubella, toxoplasmosis, syphilis) can also cause phenocopies of a number of hereditary diseases and malformations. The existence of geno- and phenocopies often makes it difficult to make a diagnosis, so the doctor should always keep their existence in mind.
31.Multiple allelism. Human blood groups according to the ABO system (genotypes, phenotypes, inheritance, transfusion rules)
. Multiple allelism - the presence in the gene pool of a population at the same time 3 or more different alleles of one gene. An example is the diversity of human eye color, the diversity of blood groups. Gene I can be represented by three different alleles: I A , I B , i , which are combined in zygotes only in pairs.
Another example is the inheritance of coat color in rabbits (Fig. 40). There are four alleles in the rabbit population.
Gene A is responsible for the inheritance of dark coat color and dominates all other alleles. Gene ach causes chinchilla coloration and in relation to genes a h And a behaves like a dominator. Gene a h responsible for the Himalayan coat color and dominates the gene a (white color). Thus, A >ach >a h >a (Table 5).
The cause of multiple allelism is random changes in the structure of the gene (mutations) that are preserved in the process of natural selection in the gene pool of the population.
The diversity of alleles that recombine during sexual reproduction determines the degree of genotypic diversity among representatives of a given species, which is of great evolutionary importance, increasing the viability of populations under changing conditions of their existence. In addition to evolutionary and ecological significance, the allelic state of genes has big influence on the functioning of the genetic material. In diploid somatic cells of eukaryotic organisms, most genes are represented by two alleles that together influence the formation of traits.
Blood groups- these are genetically inherited traits that do not change during life under natural conditions. The blood group is a certain combination of surface antigens of erythrocytes (agglutinogens) of the ABO system.
The definition of group affiliation is widely used in clinical practice in the transfusion of blood and its components, in gynecology and obstetrics in the planning and management of pregnancy.
The AB0 blood group system is the main system that determines the compatibility and incompatibility of transfused blood, since its constituent antigens are the most immunogenic. A feature of the AB0 system is that in the plasma of non-immune people there are natural antibodies to the antigen that is absent on erythrocytes. The AB0 blood group system consists of two group erythrocyte agglutinogens (A and B) and two corresponding antibodies - plasma agglutinins alpha (anti-A) and beta (anti-B).
Various combinations of antigens and antibodies form 4 blood types:
1. Group 0 (I)- there are no group agglutinogens on erythrocytes, agglutinins alpha and beta are present in plasma;
2. Group A (II)- erythrocytes contain only agglutinogen A, agglutinin beta is present in plasma;
3. Group B (III)- erythrocytes contain only agglutinogen B, plasma contains agglutinin alpha;
4. Group AB (IV)- antigens A and B are present on erythrocytes, the plasma does not contain agglutinins.
Determination of blood groups is carried out by identifying specific antigens and antibodies (double method or cross-reaction).
Questions within the paragraph: What methods of biological research underlie the study of living systems?
The scientific method is a set of actions designed to help achieve a desired result.
Methods used in biology:
A. Empirical - observation and experiment.
b. Theoretical - analysis, synthesis, generalization, modeling, mathematical processing.
Page 110. Questions and tasks after §
1. Why, in some cases, none of the allelic genes does not show its effect in the phenotype?
Allelic genes - genes located in homologous loci of chromosomes. why none of them shows its effect in the phenotype? the rule of allelic exclusion applies here - some allelic genes in the chromosome are active, and some are "turned off", and nothing can be done with them - a mutation. for example, the formation of salivary glands. if the allelic genes of this trait do not appear, a person will be born without them - however, he will not live long.
2. Explain why Mendel is considered the founder of genetics.
Mendel embarked on experiments on the inheritance of traits in a new way. He took into account the mistakes of his predecessors and came to the conclusion that it is necessary to concentrate on a specific trait, and not on the plant as a whole. Secondly, he successfully chose the object of study - peas, a self-pollinating plant that has a set of well-defined alternative traits and gives numerous offspring. Thirdly, Mendel carried out a strict accounting of the descendants obtained as a result of a certain type of crossing, which allowed him to identify the purity with which carriers of mutually exclusive (alternative) traits appear. Based on all this, he developed hybridological analysis, that is, the nature of the inheritance of traits based on the crossing system.
3. What new approaches did Mendel use in his experiments on plant hybrids?
Focusing on specific plant traits (shape, fruit color, stem type, leaf size, etc.)
A successful object of study is peas (self-pollinating, a convenient flower for artificial pollination, large chromosomes)
Statistical analysis of offspring (detailed calculation of the number of offspring with the trait in question)
AA - dominant yellow homozygous
aa - recessive green homozygous
Answer: in this crossing, the type of complete dominance of traits appeared, Mendel's I law - the uniformity of all F1 hybrids.
If the dominant trait (gene) does not completely suppress recessive trait, and both alleles show their effect. Such an intermediate dominance of a trait occurs in nature more often than complete dominance, which explains the diversity of traits on Earth.
P - parents ♂ - male, ♀ - female
G - gametes (sex cells, circled to indicate a cell)
F1 - the first generation of hybrids (descendants)
AA - dominant red homozygous snapdragon
aa - recessive white snapdragon homozygous
Answer: in this crossing, a type of incomplete dominance of traits appeared, but Mendel's law I - the uniformity of all F1 hybrids manifested itself in full, only the color is not red in hybrids, but pink, due to incomplete suppression of the recessive white trait by red.
