The methods widely used in the study of human genetics include genealogical, population-statistical, twin, dermatoglyphics, cytogenetic, biochemical, methods of somatic cell genetics.

genealogical method

The basis of this method is the compilation and analysis of pedigrees. This method is widely used from ancient times to the present day in horse breeding, selection of valuable lines of cattle and pigs, in obtaining purebred dogs, as well as in breeding new breeds of fur animals. Human genealogies have been compiled over many centuries in relation to the reigning families in Europe and Asia.

As a method of studying human genetics, the genealogical method began to be used only from the beginning of the 20th century, when it became clear that the analysis of pedigrees in which the transmission of some trait (disease) from generation to generation can be replaced by the hybridological method, which is actually inapplicable to humans.

When compiling pedigrees, the source is a person - a proband, whose pedigree is being studied. Usually this is either a patient, or a carrier of a certain trait, the inheritance of which needs to be studied. When compiling genealogical tables, the symbols proposed by G. Yust in 1931 are used (Fig. 7.24). Generations are denoted by Roman numerals, individuals in a given generation are designated by Arabic numerals.

With the help of the genealogical method, the hereditary conditionality of the studied trait can be established, as well as the type

Rice. 7.24. Conventional designations when compiling pedigrees (according to G. Yust) of its inheritance (autosomal dominant, autosomal recessive, X-linked dominant or recessive, Y-linked). When analyzing pedigrees for several traits, the linked nature of their inheritance can be revealed, which is used when compiling chromosome maps. This method makes it possible to study the intensity of the mutation process and evaluate the expressivity and penetrance of the allele. It is widely used in medical genetic counseling to predict offspring. However, it should be noted that genealogical analysis becomes much more complicated when families have few children.

The autosomal type of inheritance is generally characterized by an equal probability of occurrence of this trait in both men and women. This is due to the same double dose of genes located in the autosomes of all representatives of the species and received from both parents, and the dependence of the developing trait on the nature of the interaction of allelic genes.

When a trait dominates in the offspring of a parental pair, where at least one parent is its carrier, it manifests itself with a greater or lesser probability, depending on the genetic constitution of the parents (Fig. 7.25).

If a trait is analyzed that does not affect the viability of the organism, then the carriers of the dominant trait can be both homo- and heterozygotes. In the case of dominant inheritance of some pathological trait (disease), homozygotes, as a rule, are not viable, and carriers of this trait are heterozygotes.

Thus, with autosomal dominant inheritance, the trait can occur equally in men and women and can be traced with a sufficient number of offspring in each generation along the vertical. Analyzing pedigrees, it is necessary to remember the possibility of incomplete penetration of the dominant allele, due to the interaction of genes or environmental factors. The penetrance index can be calculated as the ratio of the actual number of carriers of a trait to the number of expected carriers of that trait in a given family. It must also be remembered that some diseases do not appear immediately from the moment of birth.

Rice. 7.25. The probability of having offspring dominant trait from various married couples (/ - III)

child. Many diseases inherited according to the dominant type develop only at a certain age. Thus, Huntington's chorea is clinically manifested by the age of 35-40, polycystic kidney disease also manifests itself late. Therefore, when predicting such diseases, brothers and sisters who have not reached a critical age are not taken into account.

The first description of a pedigree with an autosomal dominant type of inheritance of an anomaly in humans was given in 1905. It traces the transmission in a number of generations brachydactyly(short-fingered™). On fig. 7.26 shows a pedigree with this anomaly. On fig. 7.27 shows a pedigree with retinoblastoma in a case of incomplete penetrance.

Recessive traits appear phenotypically only in homozygotes for recessive alleles. These signs are usually

Rice. 7.26. Pedigree (X) with an autosomal dominant type of inheritance (brachydactyly - B)

Rice. 7.27.

Rice. 7.28. The probability of having offspring with a recessive trait from different married couples

are found in the offspring of phenotypically normal parents - carriers of recessive alleles. The probability of occurrence of recessive offspring in this case is 25%. If one of the parents has a recessive trait, then the probability of its manifestation in the offspring will depend on the genotype of the other parent. In recessive parents, all offspring will inherit the corresponding recessive trait (Fig. 7.28).

For pedigrees with an autosomal recessive inheritance pattern, it is characteristic that the trait does not appear in every generation. Most often, recessive offspring appear in parents with a dominant trait, and the likelihood of such offspring appears in closely related marriages, where both parents can be carriers of the same recessive allele obtained from a common ancestor. An example of autosomal recessive inheritance is the pedigree of a family with pseudohypertrophic progressive myopathy, in which closely related marriages are frequent (Fig. 7.29). Draws attention to the spread of the disease in the last generation horizontally.

Genes located on the X chromosome that do not have

Rice. 7.29. The pedigree in autosomal recessive inheritance (pseudohypertrophic progressive myopathy) of alleles in the Y-chromosome is presented in the genotypes of men and women in different doses. A woman receives her two X chromosomes and the corresponding genes from both her father and mother, while a man inherits his only X chromosome only from his mother. The development of the corresponding trait in men is determined by a single allele present in its genotype, while in women it is the result of the interaction of two allelic genes. In this regard, traits inherited according to the X-linked type are found in the population with different probability in males and females.

With dominant X-linked inheritance, the trait is more common in women due to their greater ability to receive the corresponding allele from either their father or mother. Men can only inherit this trait from their mother. Women with a dominant trait pass it on equally to their daughters and sons, while men only pass it on to their daughters. Sons never inherit a dominant X-linked trait from their fathers.

An example of this type of inheritance is the pedigree described in 1925 with follicular keratosis- skin disease, accompanied by loss of eyelashes, eyebrows, hair on the head (Fig. 7.30). Characteristic is a more severe course of the disease in hemizygous men than in women, who are most often heterozygotes.

In some diseases, the death of male hemizygotes is observed in the early stages of ontogeny. Then in the pedigrees among the affected should be only women, in whose offspring the ratio of affected daughters, healthy daughters and healthy sons is 1:1:1. Male dominant hemizygotes that do not die at very early stages of development are found in spontaneous abortions or among stillborns. Such features of inheritance in humans are characterized by pigmentary dermatosis.

A characteristic feature of pedigrees with this type of inheritance is the predominant manifestation of the trait in hemizygous men who inherit it from their mothers.

Rice. 7.30. Pedigree with an X-linked dominant type of inheritance (follicular keratosis)

Rice. 7.31. Pedigree with X-linked recessive inheritance (hemophilia type A)

with a dominant phenotype, which are carriers of the recessive allele. As a rule, the trait is inherited by men through the generation from maternal grandfather to grandson. In women, it manifests itself only in the homozygous state, the likelihood of which increases with closely related marriages.

The most famous example of recessive X-linked inheritance is hemophilia. The inheritance of hemophilia type A is presented in the pedigree of the descendants of the English Queen Victoria (Fig. 7.31).

Another example of inheritance by this type is color blindness- a certain form of violation of color perception.

The presence of the Y chromosome only in males explains the peculiarities of the Y-linked, or hollandic, inheritance of the trait, which is found only in men and is transmitted through the male line from generation to generation from father to son.

Rice. 7.32. Pedigree with Y-linked (Holandric) type of inheritance

One trait whose Y-linked inheritance in humans is still debated is ear hypertrichosis, or the presence of hair on the outer edge of the ear. It is assumed that in addition to this gene, the short arm of the Y chromosome contains genes that determine the male sex. In 1955, a Y-linked transplantation antigen, called HY, was described in the mouse.

Perhaps it is one of the factors of sexual differentiation of male gonads, the cells of which have receptors that bind this antigen. The receptor-bound antigen activates male-type development of the gonad (see Sections 3.6.5.2; 7.1.2).

This antigen has remained almost unchanged in the course of evolution and is found in the body of many animal species, including

and a person. Thus, the inheritance of the ability to develop gonads according to the male type is determined by the hollandic gene located on the Y chromosome (Fig. 7.32).

The genealogical method, or the method of collecting and analyzing a pedigree, is the main one in the practice of medical genetic counseling. It has been used since the end of the 19th century, developed and put into practice by the famous English researcher Francis Galton. It is based on tracing a normal or pathological trait in a series of generations related by family ties. Carried out in two stages:

1) drawing up a pedigree;

2) analysis of the pedigree.

The compilation of a pedigree begins with proband , those. the person being researched. Information about the sibs (brothers and sisters) of the proband, his parents, about the sibs of the parents and their children, etc. is recorded in the genetic map. It is very important to clarify the issue of the presence of spontaneous abortions, stillbirths and early infant mortality.

On the basis of the collected information, a graphic representation of the pedigree is prepared using conventional symbols proposed back in the early 30s of the 20th century by A. Yut. They were modified and supplemented subsequently by some other authors.

The method is used to:

1. Revealing the hereditary nature of the trait under study. If the same symptom is recorded several times in the family, then it is possible to assume the hereditary nature or family nature of the disease.

2. Definition of heterozygous carriage of the mutant gene.

3. Establishment of linked inheritance of traits.

4. Determination of gene penetrance.

5. Studying the intensity of the mutation process.

6. Establishing the type of inheritance of a monogenic disease.

Monogenic A disease caused by the action of a single pathological gene is called. Depending on what the pathological gene is (dominant or recessive) and where it is located (in the autosome or sex chromosome), five types of inheritance are distinguished:

- autosomal dominant

- autosomal recessive

- X-linked dominant,

- X-linked recessive,

- Y-linked, or hollandic.

Features characteristic of the pedigree with an autosomal dominant type of inheritance

Each sick family member usually has a sick parent.

The disease is passed from generation to generation; patients are in each generation (vertical inheritance).

Healthy parents will have healthy children (with 100% gene penetrance).

The probability of having a sick child in a family where one of the spouses is sick is 50%.

Features characteristic of the pedigree with an autosomal recessive type of inheritance

The presence of sick children in healthy parents.

Accumulation of affected individuals in one generation (horizontal inheritance).

The same frequency of lesions of men and women.

An increased percentage of inbreeding (consanguineous marriage).

Features characteristic of a pedigree with an X-linked dominant type of inheritance:

1. The birth of sick children in families where one of the spouses is sick.

2. If the father is sick, then all the daughters will be sick, and all the sons will be healthy.

3. If the mother is sick, then the probability of having a sick child is 50%, regardless of gender.

4. Persons of both sexes are ill, but the incidence of women is twice as high as that of men.

5. The disease can be traced in every generation.

Pedigree signs with X-linked recessive type of inheritance:

1. Predominant defeat of men.

2. The presence of healthy sons in sick fathers.

3. Transfer of a pathological gene from a sick father to daughters who have a high risk of having a sick son (25%).

Pedigree signs with Y-linked (holandric) type of inheritance

The trait that a father has is passed on to all his sons.

twin method

The method was proposed at the end of the 19th century by F. Galton.

Twins are born in one case out of 84 births. Of these, 1/3 falls on the birth of monozygotic twins, 2/3 - on dizygotic twins.

Monozygotic(MZ) twins develop from one egg fertilized by one sperm. Their genotype is identical, and differences between twins are determined mainly by environmental factors.

dizygotic(DZ) twins develop when two eggs are fertilized by two sperm. They have 50% common genes, like brothers and sisters born within the same married couple in different time. Differences in phenotype in DZ are determined by both genotype and environmental factors.

Twin studies are carried out in three stages.

Selection of twin pairs.

Establishment of zygosity.

Comparison of pairs of twins according to the studied characteristics.

The coincidence of the analyzed traits in twins is denoted as concordance , mismatch - discordance .

The method allows you to establish the role of heredity and environment in the development of any trait.

At the final stage of the study, the indicators of concordance of the trait between mono- and dizygotic twins are compared. If the indicators of concordance in both groups are close, this means that the leading role in the development of the trait belongs to environmental factors. The greater the difference between the concordance rates in groups of mono- and dizygotic twins, the greater the contribution to the development of traits is made by the genotype.

There is a formula by which one can determine the role of heredity and environment in the development of a trait:

% skh-va MZ -% sh-va DZ

100% - % DZ

H - coefficient of heritability.

If H \u003d 1, the sign is strictly hereditary (blood groups).

If H = 0, the trait is determined by environmental factors (infectious diseases).

If H = 0.5, the trait is determined equally by both the genotype and the environment.

Cytogenetic method

Includes two main types of research:

1) the study of the chromosome set in the somatic cells of the human body, i.e. karyotype;

2) determination of sex chromatin.

Modern clinical medicine can no longer do without genetic methods. To study hereditary traits in humans, various biochemical, morphological, immunological, and electrophysiological methods are used. Thanks to the progress of genetic technologies, laboratory genetic diagnostic methods can be performed on a small amount of material that can be sent by mail (a few drops of blood on filter paper, or even on one cell taken at an early stage of development (N. P. Bochkov, 1999) (Fig. 1.118).

Rice. 1.118. M. P. Bochkov (born in 1931)

In solving genetic problems, the following methods are used: genealogical, twins, cytogenetic, somatic cell hybridization, molecular genetic, biochemical, dermatoglyphics and palmoscopy methods, population statistical, genome sequencing, etc.

genealogical method study of human heredity

The main method of genetic analysis in humans is to compile and study the pedigree.

Genealogy is genealogy. The genealogical method is the method of pedigrees, when a trait (disease) is traced in the family, indicating family ties between members of the pedigree. It is based on a thorough examination of family members, compilation and analysis of pedigrees.

This is the most universal method for studying human heredity. It is always used when a hereditary pathology is suspected, it allows you to establish in most patients:

The hereditary nature of the trait;

Type of inheritance and allele penetrance;

The nature of the linkage of genes and carry out the mapping of chromosomes;

The intensity of the mutation process;

Deciphering the mechanisms of gene interaction.

This method used in genetic counseling.

The essence of the genealogical method is to establish family ties, symptoms or disease among close and distant, direct and indirect relatives.

It consists of two stages: drawing up a pedigree and genealogical analysis. The study of the inheritance of a trait or disease in a particular family begins with the subject who has that trait or disease.

The individual that first comes to the attention of a geneticist is called a proband. It is predominantly a patient or a carrier of exploratory signs. Children of one parental couple are called sibs of the proband (brothers - sisters). Then they go to his parents, then to the brothers and sisters of the parents and their children, then to the grandparents, etc. When compiling a pedigree, make short notes about everyone from family members, his family ties with the proband. The pedigree scheme (Fig. 1.119) is accompanied by symbols under the figure and is called a legend.

Rice. 1.119. Pedigree of the family where cataract is inherited:

patients with this disease are family members I - 1, I And - 4, III - 4,

The use of the genealogical method made it possible to establish the nature of the inheritance of hemophilia, brachydactyly, achondroplasia, etc. It is widely used to clarify the genetic nature of the pathological condition and to predict the health of offspring.

Methods of compiling pedigrees, analysis. Drawing up a pedigree begins with a proband - a personwho turned to a geneticist or a doctor and contains a trait that needs to be studied in relatives on the paternal and maternal lines.

When compiling genealogical tables, they use the conventions proposed by G. Yust in 1931 (Fig. 1.120). Pedigree figures are placed horizontally (or along circle), one line every generation. On the left, each generation is designated in Roman numerals, and individuals in a generation are designated in Arabic from left to right and from top to bottom. Moreover, the oldest generation is placed on top of the pedigree and is indicated by the number i, and the smallest is at the bottom of the pedigree.

Rice. 1.120. Symbols that are used in the compilation of pedigrees.

Brothers and sisters in connection with the birth of the eldest are located on the left. Each member of the pedigree has its own code, for example, II - 4, II And - 7. The marriage couple of the pedigree is indicated by the same number, but with a small letter. If one of the spouses is not married, the information about it is not given at all. All individuals are placed strictly by generations. If the pedigree is great, then different generations are arranged not in horizontal rows, but in concentric ones.

After drawing up the pedigree, a written explanation is attached to it - the legend of the pedigree. The following information is reflected in the legend:

Results of clinical and post-clinical examination of the proband;

Information about the personal search of relatives proband;

Comparison of the results of the personal examination of the proband according to the survey of his relatives;

Written information about relatives living in another area;

Conclusion regarding the type of disease inheritance or traits.

When compiling a pedigree, one should not be limited only to a survey of relatives - this is not enough. Some of them prescribe a complete clinical, post-clinical or special genetic examination.

The purpose of genealogical analysis is to establish genetic patterns. Unlike other methods, a genealogical survey must be completed by a genetic analysis of its results. Analysis of the pedigree makes it possible to draw a conclusion regarding the nature of the trait (hereditary or not), title, inheritance (autosomal dominant, autosomal recessive or sex-linked), zygosity of the proband (homo - or heterozygous), degree of penetrance and expressivity of the gene under study

Features of pedigrees with different types of inheritance: autosomal dominant, autosomal recessive and article-linked. An analysis of pedigrees shows that all diseases determined by the mutant gene obey the classical laws Mendel for different types inheritance.

According to the autosomal dominant type of inheritance, dominant genes are phenotypically manifested in the heterozygous state and therefore their identification and the nature of inheritance does not cause difficulties.

1) one of the parents is sick in each affected person;

2) in an affected person who is married to a healthy woman, on average, half of the children are sick, and the other half are healthy;

3) healthy children of the affected parent have healthy children and grandchildren;

4) men and women are affected equally often;

5) the disease must manifest itself in every generation;

6) heterozygous individuals affected.

An example of an autosomal dominant type of inheritance may be the nature of the inheritance of six-fingered (large-fingered). Six-fingered limbs are a rather rare phenomenon, but are persistently preserved in many generations of some families (Fig. 1.121). Bagatopalia is consistently repeated in the offspring if at least one of the parents is bugatopalia, and is absent in those cases when both parents have normal limbs. In the offspring of rich-toed parents, this trait is present in equal numbers in boys and girls. The action of this gene in ontogenesis appears quite early and has a high penetrance.

Rice. 1.121. Genus with an autosomal dominant type of inheritance.

With autosomal dominant inheritance, the risk of developing the disease in offspring, regardless of gender, is 50%, but the manifestations of the disease to a certain extent depend on penetrance.

Analysis of pedigrees shows that syndactyly, Marfan's disease, achondroplasia, brachydactyly, Osler's hemorrhagic telangiectasia, hemachromatosis, hyperbilirubinemia, hyperlipoproteinemia, various dysostoses, marble disease, osteogenesis incomplete, Recklinghausen's neurofibromatosis, otosclerosis, Peltzius-Merzbacher's disease, pelginaemia leukocytes, periodic adynamia, pernicious anemia, polydactyly, acute intermittent porphyria, hereditary ptosis, idiopathic thrombocytopenic purpura, thalassemia, tuberous sclerosis, favism, Charcot-Marie disease, Sturge-Weber disease, multiple exostoses, lens ectopia, elliptocytosis (L. O. Badalyan et al., 1971).

According to autosomal recessive inheritance, recessive genes phenotypically appear only in the homozygous state, which makes it difficult to both identify and study the nature of inheritance.

This type of inheritance is characterized by the following patterns:

1) if a sick child was born to phenotypically normal parents, then the parents are necessarily heterozygotes;

2) if the affected sibs were born from a closely related marriage, then this is evidence of the recessive inheritance of the disease;

3) if they marry a sick recessive disease and a genotypically normal person, all their children will be heterozygotes and phenotypically healthy;

4) if the marriage is ill and heterozygote, then half of their children will be affected, and half - heterozygous;

5) if two patients get married for the same recessive disease, then all their children will be sick.

6) men and women get sick with the same frequency:

7) heterozygotes are phenotypically normal, but are carriers of one copy of the mutant gene;

8) affected individuals are homozygous, and their parents are heterozygous carriers.

An analysis of pedigrees shows that the phenotype of the detection of recessive genes occurs only in those families where these genes have both parents at least in a heterozygous state (Fig. 1.122). Recessive genes in human populations remain undetected.

Rice. 1.122. Genus with an autosomal recessive type of inheritance.

However, in marriages between close relatives or in isolates (small groups of people), where marriages occur by close family ties, the expression of recessive genes increases. Under such conditions, the probability of a transition to a homozygous state and the phenotypic manifestation of rare recessive genes increases sharply.

Since most recessive genes have a negative biological significance and cause a decrease in vitality and the appearance of various virility and hereditary diseases, related marriages have a sharply negative character for the health of offspring.

Hereditary diseases are predominantly transmitted in an autosomal recessive manner, children from heterozygous parents can inherit diseases in 25% of cases (with complete penetrance). Given that complete penetrance is rare, the percentage of inheritance of the disease is also less.

По аутосомно-рецессивному типу наследуются: агаммаглобуліпемія, агранулоцитоз, алкаптонурія, альбинизм (рис. 1.123), амавротична идиотия, аміноацидурії, анемия аутоиммунная гемолитическая, анемия гипохромная мікроцитарна, анэнцефалия, галактоземия, гермафродитизм (рис 1.124), гепагоцеребральна дистрофия, болезнь Гоше, євнухоїдизм , myxedema, sickle cell anemia, fructosuria, color blindness(L. O. Badalyan et al., 1971).

Rice. 1.123. - Inheritance by autosomal recessive type. Albinism.

Rice. 1.124. Autosomal recessive inheritance. Hermaphroditism.

A number of diseases are inherited according to the X-chromosomal (sex-linked) type, when the mother is a carrier of the mutant gene, and half of her sons are sick. There are X-linked dominant X-linked recessive inheritance.

Genus of X-linked dominant inheritance (Fig. 1.125). This type of inheritance is characterized by:

1) Affected males pass on their disease to their daughters, but not to their sons;

2) affected heterozygous women transmit diseases to half of their children, regardless of their gender;

3) Affected homozygous females transmit the disease to all their children.

This type of inheritance is not common. The disease in women is not as severe as in men. It is rather difficult to distinguish between yourself X-linked dominant and autosomal dominant inheritance. The use of new technologies (DNA probes) helps to more accurately identify the type of inheritance.

Rice. 1.125. X-linked dominant inheritance.

Rodovid X-linked recessive inheritance (Fig. 1.126). This type is characterized by such inheritance patterns:

1) almost all affected are men;

2) the trait is transmitted through a heterozygous mother who is phenotypically healthy;

3) the affected father never transmits the disease to his sons;

4) all daughters of the sick father will be heterozygous carriers;

5) a carrier woman passes the disease on to half of her sons, none of the daughters will be sick, but half daughters - carriers of the hereditary gene.

Rice. 1.126. X-linked recessive inheritance.

More than 300 traits are caused by mutant genes located on the X chromosome.

An example of recessive inheritance of a sex-linked gene is hemophilia. The disease is relatively common in men and very rare in women. Phenotypically healthy women are sometimes "carriers" and, when married to a healthy man, give birth to sons with hemophilia. Such women are heterozygous for a gene that causes the loss of the ability to blood clot. From marriages of men with hemophilia to healthy women, healthy sons and carrier daughters are always born, and from marriages of healthy men to carrier women, half of the sons are sick and half of the daughters are carriers. As already noted, this is due to the fact that the father passes on his X chromosome to his daughters, and the sons receive from the father only Y -chromosome, which never contains the hemophilia gene, while their only X chromosome comes from the mother.

The following are the main diseases that are inherited in a recessive, sex-linked type.

Agammaglobulinemia, albinism (some forms), hypochromic anemia, Wiskott-Aldrich syndrome, Hutner syndrome, hemophilia A, hemophilia B, hyperparathyroidism, type VI glycogenosis, deficiency of glucose-6-phosphate dehydrogenase, nephrogenic non diabetes, ichthyosis, Lowe's syndrome, Peltzius-Merzbacher's disease, periodic paralysis, retinitis pigmentosa, pseudohypertrophic form of myopathy, Fabry's disease, phosphate diabetes, Scholz's disease, color blindness (Fig. 1.127).

Rice. 1.127. Test for determining color perception with Rabkin tables.

For genetic research, a person is an inconvenient object, since in a person: experimental crossing is impossible; a large number of chromosomes; puberty comes late; a small number of descendants in each family; equalization of living conditions for offspring is impossible.

A number of research methods are used in human genetics.

genealogical method

The use of this method is possible in the case when direct relatives are known - the ancestors of the owner of the hereditary trait ( proband) on the maternal and paternal lines in a number of generations or the descendants of the proband also in several generations. When compiling pedigrees in genetics, a certain system of notation is used. After compiling the pedigree, its analysis is carried out in order to establish the nature of the inheritance of the trait under study.

Conventions adopted in the preparation of pedigrees:
1 - man; 2 - woman; 3 - gender not clear; 4 - the owner of the studied trait; 5 - heterozygous carrier of the studied recessive gene; 6 - marriage; 7 - marriage of a man with two women; 8 - related marriage; 9 - parents, children and the order of their birth; 10 - dizygotic twins; 11 - monozygotic twins.

Thanks to the genealogical method, the types of inheritance of many traits in humans have been determined. So, according to the autosomal dominant type, polydactyly (an increased number of fingers), the ability to roll the tongue into a tube, brachydactyly (short fingers due to the absence of two phalanges on the fingers), freckles, early baldness, fused fingers, cleft lip, cleft palate, cataracts of the eyes, fragility of bones and many others. Albinism, red hair, susceptibility to polio, diabetes mellitus, congenital deafness, and other traits are inherited as autosomal recessive.

The dominant trait is the ability to roll the tongue into a tube (1) and its recessive allele is the absence of this ability (2).
3 - pedigree for polydactyly (autosomal dominant inheritance).

A number of traits are inherited sex-linked: X-linked inheritance - hemophilia, color blindness; Y-linked - hypertrichosis of the edge of the auricle, webbed toes. There are a number of genes located in homologous regions of the X and Y chromosomes, such as general color blindness.

The use of the genealogical method showed that in a related marriage, compared with an unrelated one, the likelihood of deformities, stillbirths, and early mortality in the offspring increases significantly. In related marriages, recessive genes often go into a homozygous state, as a result, certain anomalies develop. An example of this is the inheritance of hemophilia in the royal houses of Europe.

- hemophilic; - carrier woman

twin method

1 - monozygotic twins; 2 - dizygotic twins.

Children born at the same time are called twins. They are monozygotic(identical) and dizygotic(variegated).

Monozygotic twins develop from one zygote (1), which is divided into two (or more) parts during the crushing stage. Therefore, such twins are genetically identical and always of the same sex. Monozygotic twins are characterized by a high degree of similarity ( concordance) in many ways.

Dizygotic twins develop from two or more eggs that are simultaneously ovulated and fertilized by different spermatozoa (2). Therefore, they have different genotypes and can be either the same or different sex. Unlike monozygotic twins, dizygotic twins are characterized by discordance - dissimilarity in many ways. Data on the concordance of twins for some signs are given in the table.

As can be seen from the table, the degree of concordance of monozygotic twins for all the above characteristics is significantly higher than that of dizygotic twins, but it is not absolute. As a rule, the discordance of monozygotic twins occurs as a result of intrauterine development disorders of one of them or under the influence of the external environment, if it was different.

Thanks to the twin method, a person's hereditary predisposition to a number of diseases was clarified: schizophrenia, epilepsy, diabetes mellitus and others.

Observations on monozygotic twins provide material for elucidating the role of heredity and environment in the development of traits. Moreover, the external environment is understood not only as physical factors of the environment, but also as social conditions.

Cytogenetic method

Based on the study of human chromosomes in normal and pathological conditions. Normally, a human karyotype includes 46 chromosomes - 22 pairs of autosomes and two sex chromosomes. The use of this method made it possible to identify a group of diseases associated either with a change in the number of chromosomes or with changes in their structure. Such diseases are called chromosomal.

Blood lymphocytes are the most common material for karyotypic analysis. Blood is taken in adults from a vein, in newborns - from a finger, earlobe or heel. Lymphocytes are cultivated in a special nutrient medium, which, in particular, contains substances that “force” lymphocytes to intensively divide by mitosis. After some time, colchicine is added to the cell culture. Colchicine stops mitosis at the metaphase level. It is during metaphase that the chromosomes are most condensed. Next, the cells are transferred to glass slides, dried and stained with various dyes. Coloring can be a) routine (chromosomes stain evenly), b) differential (chromosomes acquire transverse striation, with each chromosome having an individual pattern). Routine staining allows you to identify genomic mutations, determine the group belonging of the chromosome, and find out in which group the number of chromosomes has changed. Differential staining allows you to identify chromosomal mutations, determine the chromosome to the number, find out the type of chromosomal mutation.

In cases where it is necessary to conduct a karyotypic analysis of the fetus, cells of the amniotic (amniotic) fluid are taken for cultivation - a mixture of fibroblast-like and epithelial cells.

Chromosomal diseases include: Klinefelter syndrome, Turner-Shereshevsky syndrome, Down syndrome, Patau syndrome, Edwards syndrome and others.

Patients with Klinefelter's syndrome (47, XXY) are always male. They are characterized by underdevelopment of the sex glands, degeneration of the seminiferous tubules, often mental retardation, high growth (due to disproportionately long legs).

Turner-Shereshevsky syndrome (45, X0) is observed in women. It manifests itself in slowing down puberty, underdevelopment of the gonads, amenorrhea (absence of menstruation), infertility. Women with Turner-Shereshevsky syndrome are small in stature, the body is disproportionate - the upper body is more developed, the shoulders are wide, the pelvis is narrow - the lower limbs are shortened, the neck is short with folds, the "Mongoloid" incision of the eyes and a number of other signs.

Down syndrome is one of the most common chromosomal diseases. It develops as a result of trisomy on chromosome 21 (47; 21, 21, 21). The disease is easily diagnosed, as it has a number of characteristic features: shortened limbs, a small skull, a flat, wide nose, narrow palpebral fissures with an oblique incision, the presence of a fold of the upper eyelid, and mental retardation. Violations of the structure of internal organs are often observed.

Chromosomal diseases also occur as a result of changes in the chromosomes themselves. Yes, deletion R-arm of autosome number 5 leads to the development of the "cat's cry" syndrome. In children with this syndrome, the structure of the larynx is disturbed, and they early childhood have a peculiar "meowing" voice timbre. In addition, there is a retardation of psychomotor development and dementia.

Most often, chromosomal diseases are the result of mutations that have occurred in the germ cells of one of the parents.

Biochemical method

Allows you to detect metabolic disorders caused by changes in genes and, as a result, changes in the activity of various enzymes. Hereditary metabolic diseases are divided into diseases of carbohydrate metabolism (diabetes mellitus), metabolism of amino acids, lipids, minerals, etc.

Phenylketonuria refers to diseases of amino acid metabolism. The conversion of the essential amino acid phenylalanine to tyrosine is blocked, while phenylalanine is converted to phenylpyruvic acid, which is excreted in the urine. The disease leads to rapid development dementia in children. Early diagnosis and diet can stop the development of the disease.

Population-statistical method

It is a method of studying the distribution of hereditary traits (inherited diseases) in populations. An essential point when using this method is the statistical processing of the obtained data. Under population understand the totality of individuals of the same species, living in a certain territory for a long time, freely interbreeding with each other, having a common origin, a certain genetic structure and, to one degree or another, isolated from other such populations of individuals of a given species. A population is not only a form of existence of a species, but also a unit of evolution, since the microevolutionary processes culminating in the formation of a species are based on genetic transformations in populations.

The study of the genetic structure of populations deals with a special section of genetics - population genetics. In humans, three types of populations are distinguished: 1) panmictic, 2) demes, 3) isolates, which differ from each other in number, frequency of intra-group marriages, the proportion of immigrants, and population growth. The population of a large city corresponds to the panmictic population. The genetic characteristics of any population includes the following indicators: 1) gene pool(the totality of genotypes of all individuals of a population), 2) gene frequencies, 3) genotype frequencies, 4) phenotype frequencies, marriage system, 5) factors that change gene frequencies.

To determine the frequencies of occurrence of certain genes and genotypes, hardy-weinberg law.

Hardy-Weinberg law

In an ideal population, from generation to generation, a strictly defined ratio of frequencies of dominant and recessive genes (1), as well as the ratio of frequencies of genotypic classes of individuals (2) is preserved.

where p— frequency of occurrence of the dominant gene A; q- the frequency of occurrence of the recessive gene a; R 2 - the frequency of occurrence of homozygotes for the dominant AA; 2 pq- frequency of occurrence of Aa heterozygotes; q 2 - the frequency of occurrence of homozygotes for the recessive aa.

The ideal population is a sufficiently large, panmictic (panmixia - free crossing) population, in which there is no mutation process, natural selection and other factors that disturb the balance of genes. It is clear that ideal populations do not exist in nature; in real populations, the Hardy-Weinberg law is used with amendments.

The Hardy-Weinberg law, in particular, is used to roughly count the carriers of recessive genes for hereditary diseases. For example, phenylketonuria is known to occur at a rate of 1:10,000 in a given population. Phenylketonuria is inherited in an autosomal recessive manner, therefore, patients with phenylketonuria have the aa genotype, that is q 2 = 0.0001. From here: q = 0,01; p= 1 - 0.01 = 0.99. Carriers of the recessive gene have the Aa genotype, that is, they are heterozygotes. The frequency of occurrence of heterozygotes (2 pq) is 2 0.99 0.01 ≈ 0.02. Conclusion: in this population, about 2% of the population are carriers of the phenylketonuria gene. At the same time, you can calculate the frequency of occurrence of homozygotes for the dominant (AA): p 2 = 0.992, just under 98%.

A change in the balance of genotypes and alleles in a panmictic population occurs under the influence of constantly acting factors, which include: the mutation process, population waves, isolation, natural selection, gene drift, emigration, immigration, inbreeding. It is thanks to these phenomena that an elementary evolutionary phenomenon arises - a change in the genetic composition of a population, which is the initial stage in the process of speciation.

Human genetics is one of the most intensively developing branches of science. It is the theoretical basis of medicine, reveals the biological basis of hereditary diseases. Knowing the genetic nature of diseases allows you to make an accurate diagnosis in time and carry out the necessary treatment.

Go to lectures №21"Variability"

Option 3. Nikishova E.A., Shatalova S.P. USE 2014

A1. The genealogical method is used in science for

1) obtaining gene and genomic mutations

2) studying the influence of upbringing on human ontogenesis
3) studies of heredity and variability

4) studying the stages of evolution of the organic world;

4) studying the stages of evolution of the organic world

A2. “Cell reproduction occurs by dividing ...” - the position of the theory

ontogenesis 3) evolutionary

cellular 4) mutational

A3. What is the function of the endoplasmic reticulum in the cell?

DNA synthesis 3) transport of substances

mRNA synthesis 4) formation of ribosomes

A4. How is a zygote different from a gamete?

double set of chromosomes

single set of chromosomes

formed as a result of meiosis

formed by mitosis

A5. Viruses and bacteria include

nucleic acids and proteins

glucose and fat

starch and ATP

water and mineral salts

A6. The similarity of the embryonic development of vertebrates indicates (about) their

metabolic ability

depending on the environment

cellular structure

A7. What types of gametes are formed in an organism with the AaBb genotype with independent inheritance of genes?

AB, ab 3) AB, Ab, aB, ab

Aa, Bb 4) AA, Bb, Aa, BB

A8. Determine the genotype of the first hybrid generation of Night Beauty plants using the incomplete dominance scheme.

A9. The appearance of black seed color in many cereals illustration

1) the rules of the ecological pyramid

2) the law of homologous series in hereditary variability

3) hypotheses of purity of gametes

4) synthetic theory of evolution

A10. The body of a lichen consists of

1) fungal hyphae and unicellular algae

2) fungal hyphae fused with plant roots

3) a variety of tissues of multicellular algae

4) filamentous algae and bacteria

A11. Through the stomata of plants

1) gas exchange

2) transport of mineral salts

3) transport of organic substances

4) heat release

A12. How are mosses classified in the plant kingdom?

1) In the process of respiration, mosses consume organic matter.

3) Moss cells have a nucleus, cytoplasm, outer cell membrane.

4) Mosses have a cellular structure and are formed by various tissues.

A13. What is the function of the cell of the inner layer of the body of the hydra, shown in the figure?

excretes into the intestinal cavity

forms intermediate cells

forms sex cells

absorbs and digests food particles

A14. To what class do vertebrates with a three-chambered heart, pulmonary and skin respiration belong?

1) Amphibians 3) Mammals

2) Cartilaginous fish 4) Reptiles

A15. In humans, when it enters the stomach, they split

1) fats 3) carbohydrates

2) proteins 4) nucleic acids

A16. When the bones move in the knee joint, friction is reduced due to

joint bag

articular ligaments

joint fluid

negative pressure inside the joint

A17. What formed elements of the blood carry oxygen from the lungs to the tissues?

1) platelets 3) lymphocytes

2) erythrocytes 4) platelets

A18. The initial link of the reflex arc in the salivary reflex is

1) salivary gland 3) intercalary neuron

2) receptor 4) motor neuron

A19. When eating meat that has not passed veterinary control, a person can become infected

1) pinworms 3) liver fluke,

2) roundworm 4) bull tapeworm

A20. An individual is classified as a single species if

they have the same set of chromosomes

biotic bonds are established between them

they live in the same environment

they have a variety of mutations

A21. The diversity of plant and animal species in nature is the result of

artificial selection

human economic activity

actions of the driving forces of evolution

modification variability

A22. The development of organisms from a single cell - evidence

relationship between organisms and environment

unity of the organic world

unity of animate and inanimate nature

diversity of the organic world

A23. A particular change in the structure of individuals of a species, contributing to adaptation to certain environmental conditions, is called

1) aromorphosis 3) convergence

2) degeneration 4) idioadaptation

A24. What is the nature of the relationship between organisms of different species that need the same food resources?

1) predator - prey 3) competition

there are power circuits

dominated by monocultures

cycling takes place

different species live

A26. The gas function of the living matter of the Earth is due to the processes

respiration and photosynthesis

growth and development

mineralization and migration of atoms

discharge and irritability

A27. In a DNA molecule, nucleotides with thymine make up 10% of the total number of nucleotides. How many nucleotides with adenine are in this molecule?
1)10% 2)40% 3)80% 4)90%

A28. The greatest amount of energy is released when one bond in a molecule is split

1) polysaccharide 3) glucose

2) protein 4) ATP

A29. Conjugation and crossing over are very important for evolution, as they contribute to

preservation of the gene pool of the population

population change

increase the viability of offspring

the emergence of new combinations of traits in a population

A30. When crossing heterozygous pea plants with yellow smooth seeds and plants with green (a) wrinkled (b) seeds, the number of phenotypes in the offspring will be equal to

1) one 3) three

2) two 4) four

A31. In animal breeding, in contrast to the breeding of plants and microorganisms, selection is carried out

1) artificial 3) exterior

2) mass 4) stabilizing

A32. An increase in the level of metabolism in vertebrates contributes to the supply of body cells with blood

1) with mixed 3) arterial

2) venous 4) saturated with carbon dioxide

A33. The breakdown of oxyhemoglobin into hemoglobin and oxygen occurs in

arteries

capillaries of the pulmonary circulation

capillaries of the systemic circulation

A34. The separation of saliva that occurs when the receptors of the oral cavity are irritated is a reflex

conditional, requiring reinforcement

unconditional, hereditary

arising during the life of man and animal

individual for each person

A35. One of the proofs of the relationship between birds and stumbling -

having two pairs of limbs

moving on land with the help of the hind limbs

dry skin without glands

missing teeth, horny sheath on the jaws

A36. Are the following judgments about the criteria for the type of organisms correct?

A. The biochemical criterion of lupine species is understood as the ability to synthesize and accumulate certain alkaloids in plants.

B. An ecological criterion is a set of environmental factors affecting organisms of the same species.

1) only A is true 3) both judgments are true

2) only B is correct 4) both judgments are wrong

IN 1. What cell structures contain circular DNA?

ribosome subunits 5) chloroplasts

nuclear chromosomes 6) mitochondria

bacterial nucleoids

microtubules of the cytoskeleton

IN 2. What features have developed in cetaceans in connection with the aquatic lifestyle?

the birth of cubs and feeding them with milk

atmospheric air breathing

streamlined body shape

transformation of the forelimbs into flippers

division of the body cavity by the diaphragm

thick layer of subcutaneous fat

AT 3. What organisms can be classified as producers?

green plants

fungi

cyanobacteria

herbivores

red algae

pathogenic prokaryotes

AT 4. Establish a correspondence between the fungus and the group of organisms to which it belongs according to the type of nutrition.

MUSHROOM GROUP

late blight

D) smut

AT 5. Establish a correspondence between the characteristics of the fabric and its type

CHARACTERISTIC

intercellular substance is practically absent

B) performs nutritional and supporting functions

lines the inside of the intestines and other organs

D) forms subcutaneous adipose tissue

D) forms the internal environment of the body

FABRIC TYPE

1) epithelial

2) connecting

AT 6. Establish a correspondence between the organoid of a eukaryotic cell and its structural features

ORGANOID

A) chloroplast

B) endoplasmic reticulum

B) lysosome

D) mitochondrion

D) Golgi complex

BUILDING FEATURES

1) single membrane

2) double membrane

AT 7. Establish a correspondence between organisms and the functional group of the biocenosis to which they belong.

FUNCTIONAL GROUP

1) producers

2) consumers

ORGANISMS

A) blue-green (cyanobacteria)

B) iron bacteria

D) nodule plants

D) weeds

AT 8. Establish the sequence of stages of plant evolution.

emergence of psilophytes

emergence of multicellular algae

the emergence of ferns

emergence of angiosperms

appearance of unicellular algae

C1. Explain why in the cells of the muscle tissue of an untrained person, after intense physical work, a feeling of pain arises.

C2. Find errors in the given text. Indicate the numbers of the sentences in which they are contained and correct them.

C3. Describe the features of the plant kingdom. Give at least four signs.

C4. Explain the reason for the great diversity of marsupials in Australia and their absence on other continents.

C5. The hormone oxytocin is a protein. 9 tRNA molecules participated in the process of translation of its molecule. Determine the number of amino acids that make up the synthetic protein, as well as the number of triplets and nucleotides that code for this protein. Explain the answer.

Sat. In sowing peas, the yellow color of the seeds dominates over the green, the convex shape of the fruit - over the fruits with constriction. When a plant with yellow convex fruits was crossed with a plant with yellow seeds and fruits with a constriction, 63 plants with yellow seeds and convex fruits were obtained, 58 with yellow seeds and fruits with a constriction, 18 with green seeds and convex fruits, and 20 with green seeds fruits with constriction. Make a scheme for solving the problem. Determine the genotypes of the original plants and descendants. Explain the emergence of different phenotypic groups.

one). Muscle cells lack oxygen

2) glycolysis occurs during which lactic acid is formed. She causes pain.

one). 1- human roundworm

2) 4- in the white planarian, the intestine opens outwards only through the mouth opening; 3) 5 - the white planaria does not have a respiratory system and gas exchange is carried out through the surface of the body.

The presence in the cells of chloroplasts, in which photosynthesis occurs;

The presence in the cells of a strong shell of fiber, which gives it a shape;

The presence of vacuoles filled with cell sap.

one). Australia separated from other continents during the heyday of marsupials before the appearance of placental animals (geographical isolation);

2). The natural conditions of Australia contributed to the divergence of signs of marsupials and active speciation;

3). On other continents, marsupials have been supplanted by other placental mammals.

one). One tRNA transports one amino acid, so 9 tRNAs will transport 9 amino acids;

2). The number of DNA triplets is 9, because one triplet encodes 1 amino acid;

3). The number of nucleotides is 27, because triplet code (9x3=27).

The scheme for solving the problem includes:

1) genotypes of initial plants: yellow seeds and convex beans AaBb (gametes AB, Ab, aB, ab) x yellow seeds and constricted beans Aabb (gametes Ab, ab);

2) offspring genotypes:

AaBb, AABb - 63 - yellow seeds, convex fruits,

Aabb, AAbb - 58 - yellow seeds, constricted fruits,

aabb - 18 - green seeds, convex fruits, aabb - 20 - green seeds, fruits with constriction;

3) the genes of the two traits are not linked, so the inheritance of the traits is independent.