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2 methods for studying human genetics. Genetics methods. Teacher's opening speech. Updating knowledge

2 methods for studying human genetics. Genetics methods. Teacher's opening speech. Updating knowledge

1. Genealogical method.

The method is based on tracing a characteristic in a number of generations, indicating family ties (drawing up a pedigree).

The collection of information begins with the proband.

Proband is a person whose pedigree needs to be compiled. The proband's brothers and sisters are called sibs.

The method includes two stages:

1. Collection of information about the family.

2. Genealogical analysis.

Special symbols are used to build a pedigree. The methods allow us to establish the type of inheritance of a trait: autosomal dominant, autosomal recessive, sex-linked.

With autosomal dominant inheritance the gene appears in a heterozygous state in individuals of both sexes; immediately in the first generation; a large number of patients, both vertically and horizontally. Freckles, brachydactyly, cataracts, brittle bones, chondrodystrophic dwarfism, and polydactyly are inherited according to this type.

With autosomal recessive inheritance the mutation gene appears only in the homozygous state in individuals of both sexes. As a rule, sick children are born to healthy parents (the gene is in a heterozygous state). The symptom does not appear in every generation. This is how the following traits are inherited: Left-handedness, red hair, blue eyes, myopathy, diabetes mellitus, phenylketonuria.

With X-linked dominant inheritance Persons of both sexes are affected; it is more common in women. This is how the following symptoms are inherited: pigmentary dermatosis, keratosis (loss of hair), blistering of the feet, brown tooth enamel.

With an X-linked recessive inheritance Mostly males are affected. Half (50%) of the boys in the family are sick; 50% of the girls are heterozygous for the mutant gene. This is how hemophilia A, Duchenne muscular dystrophy, and color blindness are inherited.

With Y-linked inheritance Only men are sick. Such signs are called holandric: syndactyly, hypertrichosis.

2. Cytogenetic method.

The method is based on microscopic examination of chromosomes, analysis of normal and pathological human karyotype. The study of the chromosome set is carried out on metaphase plates of lymphocytes and fibroblasts cultured under artificial conditions. Chromosome analysis is carried out using microscopy. To identify chromosomes, a morphometric analysis of chromosome length and the ratio of their arms (centromere index) is carried out, then karyotyping is carried out according to the Denver classification. This method allows us to establish hereditary human diseases, chromosome structures, translocations, and build genetic maps.

In 1969, T. Kasperson developed a method for differential staining of chromosomes, which made it possible to identify chromosomes by the nature of the distribution of stained segments. The heterogeneity of DNA in different areas along the length of the chromosome causes different staining of segments (hetero- and euchromatic areas). This method makes it possible to detect aneuploidies, chromosomal rearrangements, translocations, polyploidies (trisomy 13, 18, 21 - autosomes; deletions). Deletions on chromosome 5 form the “cry of the cat” syndrome; on the 18th - violation of the formation of the skeleton and mental retardation.

If the disorder concerns sex chromosomes, then the method of studying sex chromatin is used. Sex chromatin (Barr body) is a spiralized X chromosome, which is inactivated in the female body on the 16th day of embryonal development. The Barr body is disc-shaped and is found in the interophase cell nuclei of mammals and humans under the nuclear membrane. Sex chromatin can be detected in any tissue. Most often, epithelial cells of the buccal mucosa are examined (buccal scraping).

In the karyotype of a normal woman there are two X chromosomes, and one of them forms a sex chromatin body. The number of sex chromatin bodies in humans and other mammals is one less than the number of X chromosomes in an individual. In a woman with the XO karyotype, the cell nuclei do not contain sex chromatin. With trisomy (XXX) - 2 bodies are formed, i.e. using sex chromatin, determine the number of sex chromosomes in blood smears; in the nuclei of neutrophilocytes, sex chromatin bodies look like drumsticks extending from the nucleus of leukocytes.

Normally, in women, chromatin - positive nuclei is 20-40%, in men - 1-3%. Y-chromatin can also be detected in the buccal epithelium. It is an intensely luminous large chromocenter located at any point in the nucleus. Normally, in males, 20-90% of nuclei contain Y-chromatin.

3. Population statistical method.

The method allows you to calculate the frequency of heterozygous carriage of a pathological gene in human populations. Distribution of gene and chromosomal abnormalities. The method uses demographic and statistical data, the mathematical processing of which is based on the Hardy-Weinberg law.

Studying the frequency of gene distribution is important for analyzing the distribution of hereditary human diseases. It is known that the overwhelming number of recessive alleles are presented in the heterozygous state. The Hardy-Weinberg law allows us to determine the frequency of carriage of a pathological gene. For example: the frequency of albinism (aq 2) is 1:20000, i.e. q 2 aa = 1/20000, which means q = √ 1/20000 = 1/141

p + q = 1, then p = 1- q = 1 1/141= 140/141; frequency of heterozygotes (carriers of the albinism gene) 2 pq Aa = 2 x140/141 x 1/141 = 1/70.

4. Twin method.

The method is based on the study of signs changing under the influence of living conditions in mono- and dizygotic twins. In genetic studies of twins, it is necessary to study both types comparatively. This is the only way to evaluate the influence of different environmental conditions on the same genotypes (in monozygotes), as well as the manifestation of different genotypes in the same environmental conditions (in dizygotes).

The similarity of characteristics in twins is called concordance, the differences in characteristics are called discordance. Comparing the degree of similarity in two groups of twins allows us to judge the role of heredity and environment in pathological symptoms. The method is based on a comparative study of the characteristics of twins. It allows you to identify a list of diseases with a hereditary predisposition, determine the role of the environment and heredity in the manifestation of the disease. To do this, use the heredity coefficient (H) and the influence of the environment (E), which are calculated using the Holzinger formula:

Н =(%MZ - %DZ/100 - %DZ) x 100

MZ - concordance of monozygotic twins, DZ - dizygotic twins.

If the value H = 1, the trait is formed to a greater extent (100%) under the influence of hereditary factors; H = 0 - the trait is influenced by the environment (100%); H = 0.5 - same degree influence of environment and heredity.

For example: the concordance rate of monozygotic twins for the incidence of schizophrenia is 70%, and for dizygotic twins it is 13%. Then H = 70-13 / 100-13 = 57/87 = 0.65 (65%). Therefore, the predominance of heredity is 65%, and environment - 35%.

Using the method, they study:

1. The role of heredity and environment in the formation of the characteristics of an organism;

2. Specific factors that enhance or weaken the influence of the external environment;

3. Correlation of characteristics and functions;

5. Biochemical methods.

These methods are used to diagnose metabolic diseases caused by changes in the activity of certain enzymes (gene mutations). About 500 molecular diseases have been discovered using these methods.

In various types of diseases, it is possible to determine either the abnormal protein-enzyme itself or intermediate metabolic products.

The methods include several stages:

1) Identification using simple, accessible methods (express methods), qualitative reactions metabolic products in urine and blood.

2) Clarification of the diagnosis. For this purpose, precise chromatographic methods are used to determine enzymes, amino acids, carbohydrates, etc.

3) The use of microbiological tests based on the fact that some strains of bacteria can grow on media containing only certain amino acids and carbohydrates. If there is a substance required for bacteria in the blood or urine, then active growth of bacteria is observed on such a prepared substrate, which does not happen in a healthy person.

Biochemical methods are used to detect hemoglobinopathies, diseases of metabolic disorders of amino acids (phenylkentonuria, alkaptonuria), carbohydrates (diabetes mellitus, galactosemia), lipids (amaurotic idiocy), copper (Konovalov-Wilson disease), iron (hemochromatosis), etc.

6. Dermatoglyphics method.

Dermatoglyphics is a branch of genetics that studies hereditary conditioned skin reliefs on the fingers, palms and soles of the feet. These parts of the body have epidermal projections - ridges that form complex patterns. Skin patterns are strictly individual and genetically determined. The process of formation of capillary relief occurs during 3-6 months of intrauterine development. The mechanism of ridge formation is associated with the morphogenetic relationship between the epidermis and underlying tissues.

Genes that ensure the formation of patterns on the fingertips are involved in the regulation of fluid saturation of the epidermis and dermis.

Gene A - causes the appearance of an arch on the finger pad, gene W - the appearance of a curl, gene L - the appearance of a loop. Thus, there are three main types of patterns on the fingertips (Fig. 5.5). Frequency of occurrence of patterns: arcs - 6%, loops - about 60%, curls - 34%. A quantitative indicator of dermatoglyphics is the ridge count (the number of papillary lines between the delta and the center of the pattern; delta is the points of convergence of papillary lines that form a figure in the form of the Greek letter delta Δ).

On average, there are 15 - 20 ridges on one finger, on 10 fingers in men - 144.98; for women - 127.23 combs.

Palmar relief (palmoscopy) is more complex. It reveals a number of fields of pads and palmar lines. At the bases of the II, III, IY, Y fingers there are finger triradii (a, b, c, e), at the base of the palm - palmar (t). The palmar angle - a t d normally does not exceed 57 0 (Fig. 5.6).

Skin patterns are hereditary. The ridge texture of the skin is inherited polygenically.

The formation of dermatoglyphic patterns can be influenced by some damaging factors in the early stages of embryogenesis (for example, intrauterine exposure to the rubella virus produces deviations in patterns similar to Down's disease).

The dermatoglyphics method is used in clinical genetics as an additional confirmation of the diagnosis of chromosomal syndromes with karyotype changes.

7. Immunological methods.

The methods are based on studying the antigenic composition of cells and body fluids - blood, saliva, gastric juice. The most commonly used antigens are erythrocytes, leukocytes, and blood proteins. Different types of erythrocyte antigens form blood group systems - AB0, Rh - factor. Knowledge of the characteristics of blood immunogenetics is necessary during blood transfusion.

8. Ontogenetic method.

The ontogenetic method allows us to study the patterns of manifestation of traits during development. The purpose of the method is early diagnosis and prevention of hereditary diseases. The method is based on biochemical, cytogenetic and immunological methods. In the early stages of postnatal ontogenesis, diseases such as phenylketonuria, galactosemia, and Vitamin D-resistant rickets appear, the timely diagnosis of which contributes to preventive measures that reduce the pathology of the diseases. Diseases such as diabetes, gout, and alkaptonuria appear at later stages of ontogenesis. The method is of particular importance when studying the activity of genes that are in a heterozygous state, which makes it possible to identify recessive X-linked diseases. Heterozygous carriage is revealed by studying the symptoms of the disease (for anophthalmia - reduction of eyeballs); using stress tests (increased levels of phenylalanine in the blood in patients with phenylketonuria); using microscopic examination of tissue blood cells (accumulation of glycogen during glycogenosis); by using direct definition gene activity.

9. Method of somatic cell genetics.

Based on the study of hereditary material in cell clones from tissues grown outside the body on nutrient media. In this case, it is possible to obtain genes in their pure form and obtain hybrid cells. This allows us to analyze the linkage of genes and their localization, mechanisms of gene interaction, regulation of gene activity, gene mutations.

The use of anthropogenetics methods allows for a timely diagnosis of a hereditary disease.

Basic methods for studying human genetics:

Genealogical;

Twin;

Cytogenetic method;

Population statistical method;

The genealogical method is based on compiling a person’s pedigree and studying the nature of inheritance of a trait. This is the oldest method. Its essence is to establish pedigree relationships and determine dominant and recessive traits and the nature of their inheritance. This method is especially effective when studying gene mutations.

The method includes two stages: collecting information about the family as soon as possible larger number generations and genealogical analysis. A pedigree is compiled, as a rule, based on one or more characteristics. For this purpose, information is collected about the inheritance of a trait among close and distant relatives.

Representatives of one generation are placed in one row in the order of their birth.

Next, the second stage begins - analysis of the pedigree in order to establish the nature of inheritance of the trait. First of all, it is established how the trait manifests itself in representatives of different sexes, i.e. linkage of a trait to sex. Next, it is determined whether the trait is dominant or recessive, whether it is linked to other traits, etc. With a recessive nature of inheritance, the trait appears in large number individuals not in all generations. It may be absent from parents. With dominant inheritance, the trait is often found in almost all generations.

A characteristic feature of the inheritance of sex-linked traits is their frequent manifestation in persons of the same sex. If this sign is dominant, then it is more common in women. If the trait is recessive, then in this case it appears more often in men.

Analysis of numerous pedigrees and the distribution of the trait in the vast human population helped geneticists to establish the pattern of inheritance of many normal human traits, such as curly hair and hair color, eye color, freckling, earlobe structure, etc., as well as such anomalies as color blindness, sickle cell anemia, etc.

Thus, using the pedigree method, the dependence of a trait on genetic material, the type of inheritance (dominant, recessive, autosomal, linked to sex chromosomes), the presence of gene linkage, zygosity (homozygosity or heterozygosity) of family members, the probability of inheriting a gene in generations, the type of inheritance are established sign. With autosomal dominant inheritance (the appearance of a trait is associated with a dominant gene), the trait, as a rule, appears in every generation (horizontal inheritance). With autosomal recessive inheritance, the trait appears rarely, not in every generation (vertical inheritance), however, in consanguineous marriages, sick children are born more often. With sex-linked inheritance, the frequency of manifestation of a trait in individuals of different sexes is not the same.

The cytogenetic method consists of a microscopic examination of the structure of chromosomes and their number in healthy and sick people. Of the three types of mutations, only chromosomal and genomic mutations can be detected under a microscope. The simplest method is express diagnostics - studying the number of sex chromosomes using X-chromatin. Normally, in women, one X chromosome is present in the cells in the form of a chromatin body, while in men such a body is absent. With sex pair trisomy, women have two bodies, and men have one. To identify trisomy in other pairs, the karyotype of somatic cells is examined and an idiogram is compiled, which is compared with the standard one.

Chromosomal mutations involve changes in the number or structure of chromosomes. Of these, under a microscope with special staining, translocations, deletions, and inversions are clearly visible. When translocation or deletion occurs, chromosomes increase or decrease in size accordingly. And during inversion, the pattern of the chromosome changes (alternating stripes).

Chromosomal mutations can be markers in the cytogenetic method for studying a particular disease. In addition, this method is used to determine radiation doses absorbed by people and in other scientific research.

The population statistical method makes it possible to calculate the frequency of occurrence of normal and pathological genes in a population, to determine the ratio of heterozygotes - carriers of abnormal genes. By using this method the genetic structure of the population is determined (frequencies of genes and genotypes in human populations); phenotype frequencies; environmental factors that change the genetic structure of a population are studied. The method is based on the Hardy–Weinberg law, according to which the frequencies of genes and genotypes in numerous populations living in constant conditions and in the presence of panmixia (free crossings) remain constant over a number of generations. Calculations are made using the formulas: p + q = 1, p2 + 2pq + q2 = 1. In this case, p is the frequency of the dominant gene (allele) in the population, q is the frequency of the recessive gene (allele) in the population, p2 is the frequency of dominant homozygotes, q2 – recessive homozygotes, 2pq – frequency of heterozygous organisms. Using this method, it is also possible to determine the frequency of carriers of pathological genes.

Cytogenetic method. Human karyotype. Characteristics of methods for differential staining of chromosomes. Denver and Paris nomenclature. Classification of chromosomes by arm length ratio and calculation of the centromere index.

Cytogenetic method. The cytogenetic method consists of examining the chromosome set of the patient's cells under a microscope. As you know, chromosomes are in a spiral state in a cell and cannot be seen. In order to visualize chromosomes, the cell is stimulated and introduced into mitosis. In prophase of mitosis, as well as in prophase and metaphase of meiosis, chromosomes despiral and are visualized.

During visualization, the number of chromosomes is assessed and an idiogram is drawn up, in which all chromosomes are written in a certain order according to the Denver classification. Based on the idiogram, we can talk about the presence of a chromosomal aberration or a change in the number of chromosomes, and, accordingly, the presence of a genetic disease.

All methods for differential chromosome staining allow us to identify them structural organization, which is expressed in the appearance of transverse striations, different in different chromosomes, as well as some other details.

Differential staining of chromosomes. A number of staining (banding) methods have been developed to reveal a complex of transverse marks (stripes, bands) on a chromosome. Each chromosome is characterized by a specific complex of bands. Homologous chromosomes are stained identically, with the exception of polymorphic regions where different allelic variants of genes are localized. Allelic polymorphism is characteristic of many genes and occurs in most populations. Detection of polymorphisms at the cytogenetic level has no diagnostic value.

A. Q-staining. The first method of differential staining of chromosomes was developed by the Swedish cytologist Kaspersson, who used the fluorescent dye quinine mustard for this purpose. Under a fluorescence microscope, areas with unequal fluorescence intensity are visible on the chromosomes - Q-segments. The method is best suited for studying Y chromosomes and is therefore used to quickly determine genetic sex, identify translocations(exchanges of sections) between the X and Y chromosomes or between the Y chromosome and autosomes, as well as for viewing a large number of cells when it is necessary to find out whether a patient with sex chromosome mosaicism has a clone of cells bearing the Y chromosome.

B. G-staining. After extensive pretreatment, often using trypsin, the chromosomes are stained with Giemsa stain. Under a light microscope, light and dark stripes are visible on chromosomes - G-segments. Although the location of the Q segments corresponds to the location of the G segments, G staining has proven to be more sensitive and has taken the place of Q staining as the standard method for cytogenetic analysis. G-staining is best for detecting small aberrations and marker chromosomes (segmented differently from normal homologous chromosomes).

B. R-staining gives a picture opposite to G-staining. Giemsa stain or acridine orange fluorescent dye is usually used. This method reveals differences in the staining of homologous G- or Q-negative regions of sister chromatids or homologous chromosomes.

D. C-staining used to analyze the centromeric regions of chromosomes (these regions contain constitutive heterochromatin) and the variable, brightly fluorescent distal part of the Y chromosome.

D. T-staining used for analyzing chromosomal regions of chromosomes. This technique, as well as staining of nucleolar organizer regions with silver nitrate (AgNOR staining), is used to clarify the results obtained by standard chromosome staining.

The classification and nomenclature of uniformly colored human chromosomes were first adopted at an international meeting in 1960 in Denver, later slightly modified and supplemented (London, 1963 and Chicago, 1966). According to the Denver classification, all human chromosomes are divided into 7 groups, arranged in order of decreasing length and taking into account the centriole index (the ratio of the length of the short arm to the length of the entire chromosome, expressed as a percentage). Groups are designated by letters English alphabet from A to G. All pairs of chromosomes are usually numbered with Arabic numerals

In the early 70s of the 20th century, a method of differential coloring of chromosomes was developed, revealing characteristic segmentation, which made it possible to individualize each chromosome (Fig. 58). Various types segments are designated by the methods by which they are most clearly identified (Q-segments, G-segments, T-segments, S-segments). Each human chromosome contains a unique sequence of bands, which allows each chromosome to be identified. Chromosomes are maximally spiralized in metaphase, less spiralized in prophase and prometaphase, which makes it possible to distinguish a larger number of segments than in metaphase.

On the metaphase chromosome (Fig. 59) there are symbols that are usually used to indicate the short and long arms, as well as the location of regions and segments. Currently, there are DNA markers or probes that can be used to determine changes in a specific, even very small, segment in chromosomes (cytogenetic maps). At the international congress of human genetics in Paris in 1971 (Paris Conference on Standardization and Nomenclature of Human Chromosomes), a system of symbols was agreed upon for a more concise and unambiguous designation of karyotypes.
When describing a karyotype:
indicated total number chromosomes and a set of sex chromosomes, a comma is placed between them (46, XX; 46, XY);
it is noted which chromosome is extra or which is missing (this is indicated by its number 5, 6, etc., or by the letters of this group A, B, etc.); the “+” sign indicates an increase in the number of chromosomes, the “-” sign indicates the absence of this chromosome 47, XY,+ 21;
the chromosome arm in which the change occurred (lengthening of the short arm is indicated by the symbol (p+); shortening (p-); lengthening of the long arm is indicated by the symbol (q+); shortening (q-);
rearrangement symbols (a translocation is denoted by t and a deletion by del) are placed before the numbers of the chromosomes involved, and the rearranged chromosomes are enclosed in parentheses. The presence of two structurally abnormal chromosomes is indicated by a semicolon (;) or a normal fraction (15/21).

The role of the twin method in the study of heredity and environment in the formation of traits. Types of twins. The problem of predisposition to diseases. Risk factors. Genealogical method (family tree analysis). Criteria for determining the type of inheritance.

The twin method is based on the study of the phenotype and genotype of twins to determine the degree of influence of the environment on the development of various traits. Among twins, there are identical and fraternal twins.

Identical twins (identical) are formed from one zygote dividing into early stage crushing into two parts. In this case, one fertilized egg gives rise to not one, but two embryos at once. They have the same genetic material, are always the same sex, and are the most interesting to study. The similarity between these twins is almost absolute. Small differences may be explained by the influence of developmental conditions.

Fraternal twins (non-identical) are formed from different zygotes, as a result of the fertilization of two eggs by two sperm. They resemble each other no more than siblings born in different time. Such twins can be same-sex or opposite-sex.

The twin method allows you to determine the degree of manifestation of a trait in a couple, the influence of heredity and environment on the development of traits. All differences that appear in identical twins who have the same genotype are associated with the influence of external conditions. Of great interest are cases where such a couple was separated for some reason in childhood and the twins grew up and were brought up in different conditions.

The study of fraternal twins allows us to analyze the development of different genotypes under the same environmental conditions. The twin method made it possible to establish that for many diseases the environmental conditions under which the phenotype is formed play a significant role.

For example, such characteristics as blood type, eye and hair color are determined only by the genotype and do not depend on the environment. Some diseases, although caused by viruses and bacteria, depend to some extent on hereditary predisposition. Diseases such as hypertension and rheumatism are largely determined by external factors and, to a lesser extent, by heredity.

Thus, the twin method allows us to identify the role of genotype and environmental factors in the formation of a trait, for which the degrees of similarity (concordance) and differences (discordance) of monozygotic and dizygotic twins are studied and compared

The genealogical method consists of analyzing pedigrees and allows you to determine the type of inheritance (dominant
recessive, autosomal or sex-linked) trait, as well as its monogenic or polygenic character. Based on the information obtained, the probability of manifestation of the studied trait in the offspring is predicted, which is of great importance for the prevention of hereditary diseases.

Genealogical analysis is the most common, simplest and at the same time highly informative method, available to everyone who is interested in their ancestry and the history of their family

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inheritance somatic genealogical relative

Introduction

Genealogical method

Twin method

Cytogenetic method

Dermatoglyphic method

Biochemical method

Somatic cell hybridization

Simulation method

Immunogenetic method

Conclusion

Bibliography

Introduction

Human genetics is a branch of genetics that studies the patterns of inheritance and variability of traits in humans, closely related to anthropology and medicine. This branch is conventionally divided into anthropogenetics, which studies the heredity and variability of normal traits human body, and medical genetics. Human genetics is also related to evolutionary theory, as it explores the specific mechanisms of human evolution and its place in nature, together with psychology, philosophy and sociology.

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

The study of human heredity and variability is difficult due to the inability to apply many standard approaches to genetic analysis. In particular, it is impossible to carry out directed crossing or experimentally obtain mutations. Humans are a difficult subject for genetic research also because of the large number of chromosomes; puberty occurs late; small number of descendants in each family; it is impossible to equalize living conditions for offspring.

A number of research methods are used in human genetics.

Genealogical method

The use of this method is possible in the case where 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 notation system is used. After compiling the pedigree, it is analyzed in order to establish the nature of inheritance of the trait being studied.

Conventions adopted when compiling pedigrees:

1 -- man; 2 - woman; 3 -- gender is unknown; 4 - owner of the trait being studied; 5 -- heterozygous carrier of the recessive gene being studied; 6 - marriage; 7 - marriage of a man with two women; 8 - consanguineous marriage; 9 -- parents, children and their order of birth; 10 -- dizygotic twins; 11 - monozygotic twins.

Thanks to the genealogical method, the types of inheritance of many traits in humans have been determined. Thus, the autosomal dominant type inherits polydactyly (increased number of fingers), the ability to curl 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, eye cataracts, bone fragility 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 in a sex-linked manner: X-linked inheritance - hemophilia, color blindness; Y-linked - hypertrichosis of the edge of the auricle, webbed toes. There are a number of genes localized in homologous regions of the X and Y chromosomes, for example, general color blindness.

The use of the genealogical method has shown that with a related marriage, compared to an unrelated marriage, the likelihood of deformities, stillbirths, and early mortality in the offspring increases significantly. In consanguineous marriages, recessive genes often become homozygous, resulting in the development of certain anomalies. An example of this is the inheritance of hemophilia in the royal houses of Europe.

Inheritance of hemophilia in the royal houses of Europe: - hemophiliac; -- female carrier

Twin method

1 -- monozygotic twins; 2 - dizygotic twins.

Twins are children born at the same time. They are monozygotic (identical) and dizygotic (fraternal).

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

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

Signs	Concordance, %
	Monozygotic twins	Dizygotic twins
Normal
Blood type (AB0)
Eye color
Hair color
Pathological
Clubfoot
"Harelip"
Bronchial asthma

Tuberculosis
Epilepsy
Schizophrenia

As can be seen from the table, the degree of concordance of monozygotic twins for all of the above characteristics is significantly higher than that of dizygotic twins, but it is not absolute. As a rule, discordance in monozygotic twins occurs as a result of disturbances in the intrauterine development 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 determined: schizophrenia, epilepsy, diabetes mellitus and others.

Observations of 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 physical factors environment, but also 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 with either changes in the number of chromosomes or changes in their structure. Such diseases are called chromosomal.

The material for karyotypic analysis is most often blood lymphocytes. Blood is taken from a vein in adults, and from a finger, earlobe or heel in newborns. Lymphocytes are cultured in a special nutrient medium, which, in particular, contains added substances that “force” lymphocytes to intensively divide through 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. Staining can be a) routine (chromosomes are stained evenly), b) differential (chromosomes acquire cross-striations, with each chromosome having an individual pattern). Routine staining makes it possible to identify genomic mutations and determine group affiliation chromosomes, find out in which group the number of chromosomes has changed.

Differential staining allows you to identify chromosomal mutations, determine the chromosome by number, and find out the type of chromosomal mutation.

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

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

Patients with Klinefelter syndrome (47, XXY) are always men. They are characterized by underdevelopment of the gonads, degeneration of the seminiferous tubules, often mental retardation, and high growth (due to disproportionately long legs).

Turner-Shereshevsky syndrome (45, X0) is observed in women. It manifests itself in delayed puberty, underdevelopment of the gonads, amenorrhea (absence of menstruation), and infertility. Women with Turner-Shereshevsky syndrome are short, their body is disproportionate - the upper part of the 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” shape 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 signs: shortened limbs, a small skull, a flat, wide nose bridge, narrow palpebral fissures with an oblique incision, the presence of a fold in the upper eyelid, mental retardation. Disturbances in the structure of internal organs are also often observed.

Chromosomal diseases also arise as a result of changes in the chromosomes themselves. Thus, deletion of the p-arm of autosome No. 5 leads to the development of “cry of the cat” syndrome. In children with this syndrome, the structure of the larynx is disrupted, and they early childhood They have a peculiar “meowing” voice timbre. In addition, there is 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.

Dermatoglyphic method

In 1892 F. Galton, as one of the methods for studying humans, proposed a method for studying the skin ridge patterns of the fingers and palms, as well as the flexion palmar grooves. He established that these patterns are an individual characteristic of a person and do not change throughout life. Currently, the hereditary nature of skin patterns has been established, although the nature of inheritance has not been fully clarified. The trait is probably inherited in a polygenic manner. Dermatoglyphic studies are important in identifying twins. A study of people with chromosomal diseases revealed specific changes in them not only in the patterns of the fingers and palms, but also in the nature of the main flexion grooves on the skin of the palms. Dermatoglyphic changes in gene diseases have been less studied. These methods of human genetics are mainly used to establish paternity.

Study of prints of the skin pattern of the palms and feet. Given the existing individual differences in fingerprints, due to the developmental characteristics of the individual, several main classes are distinguished. Peculiar changes in fingerprints and palm patterns have been noted in a number of hereditary degenerative diseases of the nervous system. Characteristic of Down's disease is the monkey (four-fingered) fold, which is a line running across the entire palm in the transverse direction. Currently, the method is used mainly in forensic medicine.

Biochemical method

Hereditary diseases that are caused by gene mutations that change the structure or rate of protein synthesis are usually accompanied by disorders of carbohydrate, protein, lipid and other types of metabolism. Inherited metabolic defects can be diagnosed by determining the structure of the altered protein or its quantity, identifying defective enzymes, or detecting metabolic intermediates in extracellular body fluids (blood, urine, sweat, etc.). For example, analysis of the amino acid sequences of mutationally altered hemoglobin protein chains made it possible to identify several hereditary defects that underlie a number of diseases, including: hemoglobinosis. Thus, in sickle cell anemia in humans, abnormal hemoglobin due to mutation differs from normal by replacing only one amino acid (glutamic acid with valine).

In healthcare practice, in addition to identifying homozygous carriers of mutant genes, there are methods for identifying heterozygous carriers of some recessive genes, which is especially important in medical genetic counseling. Thus, in phenotypically normal heterozygotes for phenylketonuria (a recessive mutant gene; in homozygotes, the metabolism of the amino acid phenylalanine is impaired, which leads to mental retardation) after taking phenylalanine, an increased level of it in the blood is detected. In hemophilia, heterozygous carriage of a mutant gene can be determined by determining the activity of the enzyme altered as a result of the mutation.

Population statistical method

This is a method for studying the distribution of hereditary traits (hereditary diseases) in populations. An important point when using this method is statistical processing received data. A population is a collection of individuals of the same species, long time living on certain territory, 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 that culminate in the formation of a species are based on genetic transformations in populations.

Studying genetic structure A special branch of genetics deals with populations—population genetics.

There are three types of populations in humans:

1) panmictic,

3) isolates that differ from each other in numbers, frequency of intragroup marriages, proportion of immigrants, and population growth. Population large city corresponds to a panmictic population.

The genetic characteristics of any population include the following indicators:

1) gene pool (the totality of genotypes of all individuals in a population),

2) gene frequencies,

3) genotype frequencies,

4) frequencies of phenotypes, marriage system,

5) factors that change gene frequencies.

To determine the frequency of occurrence of certain genes and genotypes, the Hardy-Weinberg law is used.

Hardy-Weinberg Law

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

p + q = 1, (1)

p2 + 2pq + q2 = 1, (2)

Where p -- frequency occurrence dominant gene A; q -- frequency occurrence recessive gene A; p2 -- frequency occurrence homozygotes By dominant AA; 2pq -- frequency occurrence heterozygotes Aa; q2 -- frequency occurrence homozygotes By recessive ah.

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 approximate the number of carriers of recessive genes for hereditary diseases. For example, phenylketonuria is known to occur at a frequency of 1:10,000 in this population. Phenylketonuria is inherited in an autosomal recessive manner, therefore, patients with phenylketonuria have the aa genotype, that is, q2 = 0.0001. Hence: q = 0.01; p = 1 - 0.01 = 0.99. Carriers of the recessive gene have the genotype Aa, that is, they are heterozygotes. The frequency of occurrence of heterozygotes (2pq) 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 by dominant (AA): p2 = 0.992, slightly less than 98%.

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

Comparative genetic method

One of the methods of human genetics is the comparative genetic method, or biomodeling method, theoretical basis which is the law homologous series hereditary variability.

This method is based on the use of laboratory animals with which experiments can be carried out, including targeted crossbreeding, administration of chemicals, irradiation and dissection at the required time. Since mammals have a large number of “common” (identical in origin) genes, information obtained in experiments on animals can be transferred to humans.

The comparative genetic method is of particular importance in medical genetics, where it makes it possible to determine the genetic causes and mechanisms of development of hereditary human diseases that are also found in animals, and to develop methods of treating them using animals. On various types animals (mice, rats, dogs, cats, rabbits, pigs, large and small cattle, etc.) models of human diseases such as hemophilia (low degree of blood clotting), phenylketonuria (increased concentration of phenylpyruvic acid in urine and blood plasma, leading to dementia), various anemia (anemia), atherosclerosis (deposition of lipids on the walls of blood vessels), hypertension (high blood pressure), obesity, breast cancer, etc.

Somatic cell hybridization

Using these methods, the heredity and variability of somatic cells are studied, which compensates for the impossibility of applying hybridological analysis to humans. These methods, based on the reproduction of these cells in artificial conditions, analyze genetic processes in individual cells of the body, and, thanks to the usefulness of the genetic material, use them to study the genetic patterns of the whole organism.

Hybrid cells containing 2 complete genomes usually “lose” chromosomes of preferably one of the species when dividing. Thus, it is possible to obtain cells with the desired set of chromosomes, which makes it possible to study the linkage of genes and their localization on certain chromosomes.

Thanks to the methods of somatic cell genetics, it is possible to study the mechanisms of primary action and interaction of genes, the regulation of gene activity. The development of these methods has determined the possibility accurate diagnosis hereditary diseases in the prenatal period.

Simulation method

Studies human diseases in animals that can suffer from these diseases. It is based on Vavilov’s law on homologous series of hereditary variability, for example, sex-linked hemophilia can be studied in dogs, epilepsy in rabbits, diabetes mellitus, muscular dystrophy in rats, cleft lip and palate in mice.

Models in biology are used to model biological structures, functions and processes in different levels organization of living things: molecular, subcellular, cellular, organ-systemic, organismal and population-biocenotic. It is also possible to model various biological phenomena, as well as the living conditions of individuals, populations and ecosystems.

In biology, mainly three types of models are used: biological, physicochemical and mathematical (logical-mathematical).

Biological models reproduce in laboratory animals certain conditions or diseases found in humans or animals. This allows us to study experimentally the mechanisms of occurrence of a given condition or disease, its course and outcome, and influence its course. Examples of such models are artificially induced genetic disorders, infectious processes, intoxication, reproduction of hypertensive and hypoxic conditions, malignant neoplasms, hyperfunction or hypofunction of certain organs, as well as neuroses and emotional states. To create a biological model, use various ways effects on the genetic apparatus, infection by microbes, introduction of toxins, removal of individual organs or introduction of their waste products (for example, hormones), various influences to central and peripheral nervous system, exclusion of certain substances from food, placement in an artificially created habitat and many other methods. Biological models are widely used in genetics, physiology, and pharmacology.

Immunogenetic method

The immunological (serological) method includes the study of blood serum, as well as other biological substrates to identify antibodies and antigens.

There are serological reactions and immunological methods using physical and chemical labels. Serological reactions are based on the interaction of antibodies with antigens and registration of accompanying phenomena (agglutination, precipitation, lysis). In immunological methods, physical and chemical labels are used that are included in the formed antigen-antibody complex, allowing the formation of this complex to be recorded.

Classical serodiagnosis is based on the determination of antibodies to an identified or suspected pathogen. A positive reaction result indicates the presence of antibodies to pathogen antigens in the blood serum being tested; a negative result indicates the absence of such.

Serological reactions are semi-quantitative and allow one to determine the antibody titer, i.e. the maximum dilution of the test serum in which a positive result is still observed.

The detection of antibodies to the causative agent of a number of infectious diseases in the blood serum being tested is not sufficient to make a diagnosis, since it may reflect the presence of post-infectious or post-vaccination immunity. That is why paired sera are examined - taken in the first days of the disease and after 7-10 days. In this case, the increase in antibody titer is assessed. A diagnostically significant increase in antibody titer in the test blood serum relative to the initial level is 4 times or more. This phenomenon is called seroconversion.

In exotic infectious diseases, as well as in hepatitis, HIV infection and some other diseases, the very fact of detecting antibodies indicates that the patient is infected and has diagnostic value.

Conclusion

Advances in the development of human genetics have made it possible to prevent and treat hereditary diseases. One of effective methods their warnings are medical and genetic counseling with prediction of the risk of the patient appearing in the offspring of persons suffering from this disease or having a sick relative.

Advances in human biochemical genetics have revealed the root cause (molecular mechanism) of many hereditarily determined defects and metabolic abnormalities, which has contributed to the development of rapid diagnostic methods that allow patients to be quickly and early identified, and the treatment of many previously incurable hereditary diseases. Most often, treatment consists of introducing into the body substances that are not formed in it due to a genetic defect, or in preparing special diets from which substances that have a toxic effect on the body as a result of a hereditary inability to break them down are eliminated.

Many genetic defects are corrected with timely surgical intervention or pedagogical correction.

Practical measures aimed at maintaining human hereditary health and protecting the gene pool of humanity are carried out through a system of medical genetic consultations. Their main goal is to inform interested parties about the likelihood of the risk of the appearance of patients in the offspring. Medical genetic activities also include the promotion of genetic knowledge among the population, as this promotes a more responsible approach to childbearing. Medical genetic consultation refrains from coercive or encouraging measures in matters of childbirth or marriage, taking on only the function of information. Great importance has a system of measures aimed at creating the best conditions for the manifestation of positive hereditary inclinations and preventing harmful effects environment on human heredity.

Human genetics represents the natural scientific basis for the fight against racism, convincingly showing that races are forms of human adaptation to specific environmental conditions (climatic and other), that they differ from each other not by the presence of “good” or “bad” genes, but by frequency the spread of common genes common to all races. Human genetics shows that all races are equivalent (but not the same) from a biological point of view and have equal opportunities for development, determined not by genetic, but by socio-historical conditions. The statement of biological hereditary differences between individuals or races cannot serve as a basis for any moral, legal or social conclusions that infringe on the rights of these individuals or races.

Bibliography

1. Fundamentals of ecology./ ed. Obukhova V. L. and Sapunova V. B. S.-Pb: Special literature, 1998.

2. Ruzavin G. I. Concepts modern natural science. M.: Unity, 2010.

3. Sheppard F. M. Natural selection and heredity. M.: Education, 2009.

4. . http://schools.keldysh.ru/sch1952/Pages/Timokhina04/Biolog/18.htm.

5. . http://www.licey.net/bio/biology/lection22.

6. . https://sites.google.com/site/biologiasch88/u/sipicyna-a-i-orlova-t/metody-genetiki.

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Features and methods of studying human genetics. Inheritance individual characteristics person. Autosomal dominant type of inheritance. Sex-linked traits. Conventions adopted for compiling pedigrees. Chromosomal diseases.

Genealogical method proposed in 1883 by F. Galton. This is a method of analyzing pedigrees (tracing the inheritance of a normal or pathological trait in a family, indicating the type of family ties between members of the pedigree). In medical genetics it is called clinical and genealogical , since pathological signs are traced and clinical research methods are applied.

The essence of the method : identification of family ties and tracing of the studied trait among close, distant, direct and indirect relatives.

Stages of the method :

1. Collecting information about relatives from the proband (a person who consulted a geneticist).

2. Drawing up a pedigree.

3. Pedigree analysis.

The method is used to establish the hereditary nature of a trait, type of inheritance, genotypes of pedigree members, and gene penetrance.

To construct genealogies, a system of symbols is used, proposed in 1931 by the English scientist Just (Fig. 17).

When constructing pedigrees, the following rules must be observed:

· it is necessary to find out the number of generations from the collected history;

· pedigree begins with the proband;

· each generation is numbered with Roman numerals on the left;

· symbols denoting individuals of the same generation are located on a horizontal line and numbered in Arabic numerals.

Pedigree analysis reveals the following types of inheritance traits: autosomal dominant; autosomal recessive; X-linked (sex-linked) dominant; X-linked (sex-linked) recessive; holandric (linked to the Y chromosome).

Autosomal dominant type of inheritance:

· A sick child is born to sick parents with a 100% probability if they are homozygous; 75% if they are heterozygous.

Figure 17. Symbolism used in compiling pedigrees

Autosomal recessive type of inheritance:

· Both men and women are affected equally.

· The probability of having a sick child from healthy parents is 25% if they are heterozygous; 0% if both or one of them is homozygous for the dominant gene.

· Often manifests itself in consanguineous marriages.

X-linked (sex-linked) dominant type of inheritance:

· Sick people occur in every generation.

· Women are more affected.

· If a father is sick, then all his daughters are sick.

· A sick child is born to sick parents with a 100% probability if the mother is homozygous; 75% if the mother is heterozygous.

· The probability of having a sick child from healthy parents is 0%.

X-chromosome (sex-linked) recessive type of inheritance:

· Patients do not occur in every generation.

· Mostly men are affected.

· The probability of having a sick boy born to healthy parents is 25%, and a sick girl is 0%.

Holandric (Y-linked) type of inheritance:

· Sick people occur in every generation.

· Only men get sick.

· If a father is sick, then all his sons are sick.

· The probability of having a sick boy from a sick father is 100%

Twin method(proposed in 1876 by F. Galton to study genetic patterns in twins.

The essence of the method : comparison of characteristics in different groups of twins based on their similarities (concordance) or differences (discordance).

Stages of the method:

1. Compiling a sample of twins from the entire population.

2. Diagnosis of zygosity of twins.

3. Establishing the relative role of heredity and environment in the formation of a trait.

To assess the role of heredity and environment in the formation and development of a trait, they use Holzinger formula:

N = ( KMB%-KDB%)/100%-KDB%

where N is the proportion of hereditary factors,

KMB% and - concordance of monozygotic twins in percentage

KDB% – concordance of dizygotic twins as a percentage

If H is greater than 0.5, then the genotype plays a large role in the formation of the trait; if H is less than 0.5, then the environment plays a large role.

Cytogenetic method is the study of karyotype using microscopy.

Stages of the method:

1. Obtaining and culturing cells (lymphocytes, fibroblasts) on artificial nutrient media.

2. Addition of phytohemagglutinin to the nutrient medium to stimulate cell division.

3. Stopping cell division at the metaphase stage by adding colchicine.

4. Treatment of cells with a hypotonic solution NaCl, as a result of which the cell membrane is destroyed and a “scattering” of chromosomes is obtained.

5. Staining of chromosomes with specific dyes.

6. Microscoping and photographing chromosomes.

7. Drawing up an idiogram and its analysis.

The method allows:

· diagnose genomic and chromosomal mutations;

Determine the genetic sex of the organism.

Biochemical methods. The cause of most hereditary monogenic diseases is metabolic defects associated with enzymopathies (disturbances in the structure of enzymes involved in metabolic reactions). At the same time, intermediate metabolic products accumulate in the body, therefore, by determining them or the activity of enzymes using biochemical methods, it is possible to diagnose hereditary metabolic diseases (gene mutations). Quantitative biochemical methods (stress tests) make it possible to identify heterozygous carriage of a pathological recessive gene.

Dermatoglyphic analysis is the study of human ridge skin (skin of the fingertips, palmar side of the hands and plantar side of the feet), where the papillary layer of the dermis is strongly pronounced.

The method is applied:

a) to establish the zygosity of twins;

b) as an express method for diagnosing the congenital component of some hereditary diseases.

Typically, with genomic pathology, a combination of certain indicators is noted: radial loops on the 4th and 5th fingers, four-digit groove, main palmar angle from 60° to 80°, etc.

Chemical methods based on quality color chemical reactions. Used for preliminary diagnosis of hereditary metabolic diseases. As a screening test diagnosis of phenylketonuria The method of wetting strips of paper soaked in a 10% solution of PeCl 3 or 2,4 dinitrophenyl-hydrazine with the child’s urine is used. If phenylpyruvic acid is present in the urine, a greenish color appears on the filter paper.

Determination of X- and Y-sex chromatin. Buccal epithelial cells or leukocytes are used for research. A"-chromatin is determined by staining the preparation acetorcein, and U-chromatin - when stained Acrichinipritom. These methods make it possible to identify the number of sex chromosomes in a karyotype (the number of A"-chromosomes is always one more than the number of A1-chromatin clumps, the number of Y-chromosomes is equal to the number of Y-chromatin clumps); establish the genetic sex of an individual, diagnose chromosomal diseases of sex (in combination with other methods).

Methods of prenatal (prenatal) diagnostics hereditary diseases make it possible to identify hereditary defects of the fetus in the early stages of pregnancy. With their help, it is possible to determine the disease long before the birth of the child, and if it is necessary to terminate the pregnancy.

The main indicators for prenatal diagnosis are:

· Well-established hereditary disease in the family.

· Mother's age is over 35 years, father's age is over 40 years.

· Presence of a sex-linked disease in the family.

· The presence of structural chromosome rearrangements in one of the parents (especially translocations and inversions).

· Heterozygosity of both parents for one pair of alleles in an autosomal recessive disease.

· The pregnant woman has a history of long-term work in hazardous industries or living in places with high background radiation, etc.

· Repeated spontaneous abortions or the birth of a child with congenital malformations, diabetes mellitus, epilepsy, infections in a pregnant woman, drug therapy.

Prenatal diagnostic methods can be divided into:

1) Screening: allow us to identify women who have an increased risk of having a child with a congenital pathology or hereditary disease. The methods are widely available and relatively inexpensive. Sifting methods include:

Determination of α-fetoprotein (AFP) concentration;

Determination of the level of human chorionic gonadotropin (hCG);

Determination of the level of unbound estriol;

Detection of pregnancy-associated plasma protein A;

Isolation of fetal cells or DNA from the mother's body.

2) Non-invasive: methods of examining the fetus without surgery. Currently, these include fetal ultrasound (US). Ultrasound can be used for both screening and clarifying methods. Accumulated evidence shows that ultrasound does not harm the fetus. In some countries, ultrasound is performed on all pregnant women. This makes it possible to prevent the birth of 2-3 children with serious congenital malformations per 1,000 newborns, which is approximately 30% of all children with such a pathology.

3) Invasive: methods based on the analysis of genetic material of fetal cells or tissues. They are carried out according to strict indications. Invasive methods include:

Biopsy of the chorion and placenta (for cytogenetic, biochemical studies and DNA analysis);

Amniocentesis (sampling of fetal amniotic fluid to diagnose gene, chromosomal and genomic mutations);

Cordocentesis (taking blood from the umbilical cord for the purpose of early diagnosis of hereditary blood diseases);

Fetoscopy (introduction of a fiberoptic endoscope into the amnion cavity to examine the fetus, placenta, umbilical cord, etc.);

Nowadays, genetics is very relevant in scientific fields for research. The impetus for its development was the well-known doctrine of Charles Darwin about the discreteness of heredity, natural selection and mutational changes due to transmission of the carrier genotype. Having begun its development at the beginning of the last century, genetics as a science has reached a wide scale, while research methods this moment are one of the main areas of study of both human nature and living nature in general.

Let us consider the fundamental methods of genetic research that are currently known.

human genetics research represent the analysis and determination of typical gene structures during inheritance in pedigrees. The results and information obtained are used to prevent, prevent and identify the likelihood of the occurrence of the studied trait in the offspring - hereditary diseases. The type of inheritance can be autosomal (the manifestation of the trait is possible with equal probability in individuals of both sexes) and linked to the chromosomal sex series of the carrier.

The autosomal method, in turn, is divided into autosomal dominant inheritance (the dominant allele can be realized in both homozygous and heterozygous states) and autosomal recessive inheritance (the recessive allele can be realized only in the homozygous state). With this type of inheritance, the disease manifests itself after several generations.

Sex-linked heredity is characterized by the localization of the corresponding gene in homologous and non-homologous regions of the Y- or X-chromosomes. Based on the genotypic background, which is localized in the sex chromosomes, a hetero- or homozygous woman is determined, but men with only one X chromosome can only be hemizygous. For example, a heterozygous woman can inherit the disease to both her son and daughters.

genetics research is determined by the study of hereditary diseases transmitted as a result of gene mutations. Such methods of studying human genetics identify hereditary metabolic defects by identifying enzymes, carbohydrates and other metabolic products that remain in the extracellular fluid of the body (blood, sweat, urine, saliva, etc.).

Twin methods for studying human genetics find out the hereditary cause of the studied signs of the disease. (a complete organism develops from two or more crushed parts of the zygote at an early stage of its development) have an identical genotype, which makes it possible to identify differences as a result of the external influence of the environment on the human phenotype. Fraternal twins (fertilization of two or more eggs) have the genotype of people related to each other, which makes it possible to evaluate environmental and hereditary factors in the development of a person’s genotypic background.

genetics research used in studying the morphology of chromosomes and the normality of the karyotype, which makes it possible to diagnose hereditary diseases at the chromosomal level when identifying genomic and chromosomal mutations, as well as to study the mutagenic effect of chemicals, pesticides, drugs, etc. This technique is widely used in the analysis and subsequent identification of hereditary abnormalities of the body even before the birth of a child. Prenatal diagnosis of amniotic fluid makes a diagnosis already in the first trimester of pregnancy, which makes it possible to make a decision to terminate the pregnancy.