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The importance of genetics for medicine and healthcare. The subject and objectives of genetics, its significance for medicine The role of genetics for practical healthcare

Subject and tasks of human genetics. Human genetics, or medical genetics, studies the phenomena of hereditary variability in various human populations, features of the manifestation and development of normal (physical, creative, intellectual abilities) and pathological characteristics, the dependence of diseases on genetic predetermination and environmental conditions, including social living conditions . The formation of medical genetics began in the 30s. XX century, when facts began to appear confirming that the inheritance of traits in humans is subject to the same laws as in other living organisms.

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The importance of genetics for medicine.

Subject and tasks of human genetics. Human genetics, or medical genetics, studies the phenomena of hereditary variability in various human populations, features of the manifestation and development of normal (physical, creative, intellectual abilities) and pathological characteristics, the dependence of diseases on genetic predetermination and environmental conditions, including social living conditions . The formation of medical genetics began in the 30s. XX century, when facts began to appear confirming that the inheritance of traits in humans is subject to the same laws as in other living organisms.

The task of medical genetics is to identify, study, prevent and treat hereditary diseases.

Methods for studying human heredity. When studying human heredity and variability, the following methods are used: genealogical, twin, cytogetic, biochemical, dermatoglyphic, somatic cell hybridization, modeling, etc.

Genealogical method allows you to find out family ties and trace the inheritance of normal or pathological characteristics among close and distant relatives in a given family based on the compilation of a pedigree-genealogy. If there are pedigrees, then, using summary data for several families, it is possible to determine the type of inheritance of a trait - dominant or recessive, sex-linked or autosomal, as well as its monogenic or polygenic nature. The genealogical method has proven the inheritance of many diseases, such as diabetes, schizophrenia, hemophilia, etc.

The genealogical method is used for diagnosing hereditary diseases and medical genetic counseling; it allows for genetic prevention (prevention of the birth of a sick child) and early prevention of hereditary diseases.

The twin method consists of studying the development of traits in twins. It allows you to determine the role of the genotype in the inheritance of complex traits, as well as assess the influence of factors such as upbringing, training, etc.

It is known that human twins are identical (monozygotic) and fraternal (dizygotic). Monozygotic, or identical, twins develop from one egg fertilized by one sperm. They are always the same sex and are strikingly similar to each other, since they have the same genotype. In addition, they have the same blood type, the same fingerprints and handwriting, they are confused by their parents and cannot be distinguished by the smell of the dog. Only identical twins are 100% successful in organ transplantation, since they have the same set of proteins and the transplanted tissue is not rejected. The proportion of identical twins in humans is about 35-38% of the total number.

Fraternal, or dizygotic, twins develop from two different eggs, simultaneously fertilized by different sperm. Dizygotic twins can be either the same or different sexes, and from a genetic point of view they are no more similar than ordinary brothers and sisters.

The study of identical twins throughout life, especially if they live in different socio-economic and climatic conditions, is interesting because the differences between them in the development of physical and mental properties are explained not by different genotypes, but by the influence of environmental conditions.

Cytogenetic method based on a microscopic study of chromosome structure in healthy and sick people. Cytogenetic control is used in the diagnosis of a number of hereditary diseases associated with aneuploidy and various chromosomal rearrangements. It also makes it possible to study tissue aging based on studies of the age-related dynamics of cell structure, to establish the mutagenic effect of environmental factors on humans, etc.

In recent years, the cytogenetic method has acquired great importance in connection with the possibilities of human genetic analysis, which were opened by the hybridization of somatic cells in culture. Obtaining interspecies hybrids of cells (for example, human and mouse) allows us to get much closer to solving problems associated with the impossibility of directed crosses, localizing a gene on a specific chromosome, establishing a linkage group for a number of traits, etc. Combining the genealogical method with the cytogenetic method, and Also, with the latest methods of genetic engineering, the process of mapping genes in humans has significantly accelerated.

Biochemical methods studies of human heredity help to detect a number of metabolic diseases (carbohydrate, amino acid, lipid, etc.) using, for example, the study of biological fluids (blood, urine, amniotic fluid) through qualitative or quantitative analysis. The cause of these diseases is a change in the activity of certain enzymes.

Using biochemical methods, about 500 molecular diseases resulting from the manifestation of mutant genes have been discovered. In various types of diseases, it is possible to either determine the abnormal protein-enzyme itself or identify intermediate metabolic products. Based on the results of biochemical tests, it is possible to diagnose the disease and determine treatment methods. Early diagnosis and the use of various diets in the first stages of postembryonic development can cure some diseases or at least alleviate the condition of patients with defective enzyme systems.

Like any other discipline, modern human genetics uses methods of related sciences: physiology, molecular biology, genetic engineering, biological and mathematical modeling, etc. A significant place in solving problems of medical genetics is occupied by ontogenetic method, which allows us to consider the development of normal pathological signs during the individual development of the organism.

Hereditary human diseases, their treatment and prevention. To date, more than 2 thousand have been registered. hereditary human diseases, most of them associated with mental disorders. According to the World Health Organization, thanks to the use of new diagnostic methods, an average of three new hereditary diseases are registered annually, which are encountered in the practice of a doctor of any specialty: therapist, surgeon, neurologist, obstetrician-gynecologist, pediatrician, endocrinologist, etc. There are practically no diseases that have absolutely nothing to do with heredity. The course of various diseases (viral, bacterial, mycoses and even injuries) and recovery from them to one degree or another depend on the hereditary immunological, physiological, behavioral and mental characteristics of the individual.

Conventionally, hereditary diseases can be divided into three large groups: metabolic diseases, molecular diseases, which are usually caused by gene mutations, and chromosomal diseases.

Gene mutations and metabolic disorders. Gene mutations can result in increased or decreased activity of certain enzymes, or even their absence. Phenotypic such mutations manifest themselves as hereditary metabolic diseases, which are determined by the absence or excess of the product of the corresponding biochemical reaction.

Gene mutations are classified according to their phenotypic manifestation, i.e. as diseases associated with disorders of amino acid, carbohydrate, lipid, mineral metabolism, and nucleic acid metabolism.

An example of a disorder of amino acid metabolism is albinism, a relatively harmless disease occurring in Western Europe with a frequency of 1:25,000. The cause of the disease is a defect in the tyrosinan enzyme, which blocks the conversion of tyrosine to melanin. Albinos have milky skin, very light hair, and no pigment in the iris. They have increased sensitivity to sunlight, which causes educational skin diseases in them.

One of the most common diseases of carbohydrate metabolism is diabetes mellitus This disease is associated with a deficiency of the hormone insulin, which leads to disruption of glycogen formation and increased blood glucose levels.

A number of pathological signs (hypertension, atherosclerosis, gout, etc.) are determined not by one, but by several genes (the phenomenon of polymerization). These are diseases with a hereditary predisposition, which largely depend on environmental conditions: under favorable conditions, such diseases may not manifest themselves.

Chromosomal diseases. This type of hereditary disease is associated with changes in the number or structure of chromosomes. The frequency of chromosomal abnormalities in newborns ranges from 0.6 to 1%, and at the stage of 8-12 weeks about 3% of embryos have them. Among spontaneous miscarriages, the frequency of chromosomal abnormalities is approximately 30%, and in the early stages (up to two months) - 50% and higher.

All types of chromosomal and genomic mutations have been described in humans, including aneuploidy, which can be of two types: monosemy and polysemy. Monosemy is particularly severe.

Whole-organism monosemy has been described for the X chromosome. This is Shereshevsky-Turner syndrome (44+X), which manifests itself in women who are characterized by pathological changes in physique (short stature, short neck), disturbances in the development of the reproductive system (absence of most female secondary sexual characteristics), and mental limitations. The frequency of occurrence of this anomaly is 1: 4000-5000.

Trisomic women(44+XXX), as a rule, are distinguished by disorders of sexual, physical and mental development, although in some patients these signs may not appear. There are known cases of fertility in such women. The frequency of the syndrome is 1:1000.

Men with Klinefelter's syndrome(44+XXY) are characterized by impaired development and activity of the gonads, a eunuchoid body type (shoulders narrower than the pelvis, hair growth and fat deposition on the body according to the female type, elongated arms and legs compared to the body). Hence the higher growth. These signs, combined with some mental retardation, appear in a relatively normal boy, starting from puberty.

Klinefelter syndrome is observed with polysomy not only on the X chromosome (XXX XXY, XXXXY), but also on the Y chromosome (XYY. XXYYY. XXYY). The frequency of the syndrome is 1:1000.

Among the autosomal diseases, the most studied is trisomy on the 21st chromosome, or Down syndrome. According to various authors, the birth rate of children with Down syndrome is 1:500-700 newborns, and over the past decades the frequency of trisomy-21 has increased.

Typical signs of patients with Down syndrome: a small nose with a wide flat bridge, slanted eyes with an epicanthus-overhanging fold over the upper eyelid, deformed small ears, a half-open mouth, short stature, mental retardation. About half of the patients have heart and large vessel defects.

There is a direct relationship between the risk of having children with Down syndrome and the age of the mother. It has been established that 22-40% of children with this disease are born to mothers over 40 years of age (2-3% of women of childbearing age).

Here we consider only a few examples of human genetic and chromosomal diseases, which, however, give a certain idea of the complexity and fragility of its genetic organization.

The main way to prevent hereditary diseases is their prevention. For this purpose, in many countries of the world there is a network of institutions providing medical and genetic counseling to the population. First of all, its services should be used by persons entering into marriage who have genetically disadvantaged relatives.

Genetic consultation is mandatory for the marriage of relatives, persons over 30-40 years of age, as well as those working in production with hazardous working conditions. Doctors and geneticists will be able to determine the degree of risk of giving birth to genetically inferior offspring and ensure monitoring of the child during its intrauterine development. It should be noted that smoking, alcohol and drug use by the mother or father of the unborn child sharply increases the likelihood of having a baby with severe hereditary diseases.

If a sick child is born, drug, dietary and hormonal treatment is sometimes possible. A clear example confirming the capabilities of medicine in the fight against hereditary diseases is polio. This disease is characterized by a hereditary predisposition, but the direct cause of the disease is a viral infection. Carrying out mass immunization against the causative agent of the disease made it possible to save all children hereditarily predisposed to it from the severe consequences of the disease. Dietary and hormonal treatment has been successfully used in the treatment of phenylketonuria, diabetes mellitus and other diseases.

Human genetics is of great importance for medicine, since about 5% of newborns are born with one or another genetically determined developmental disorder. Currently, more than 5 thousand forms of genetically determined human diseases are already known. The role of genetics in the study of human hereditary diseases and methods of their prevention, treatment, as well as ways to prevent the harmful effects of adverse environmental factors on heredity is obvious. 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 due to late puberty and the small number of offspring. Nevertheless, in human genetics methods have been developed and successfully used to study hereditary human diseases.

Genealogical method

It consists of studying pedigrees based on Mendelian laws of inheritance. This method makes it possible to establish the nature of inheritance of a trait (autosomal, sex-linked, dominant or recessive), as well as its monogenic or polygenic nature. 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. Figure 15.1 shows the conventions used in compiling pedigrees. Pedigree analysis is important for assessing the risk of manifestation of a hereditary disease in a specific member of a particular family, i.e. necessary when conducting medical genetic counseling.

Rice. 15.1.

At autosomal inheritance the symptom is characterized by an equal probability of manifestation in men and women. Autosomal dominant inheritance - the dominant allele is realized into a trait in both the dominant homozygous and heterozygous states. If at least one parent has a dominant trait, the latter manifests itself with varying probability in all subsequent generations (Fig. 15.2). However, dominant mutations are characterized by low penetrance. In some cases, this creates certain difficulties in determining the type of inheritance.

Rice. 15.2. Autosomal dominant type of inheritance. I- IV - number of generations

At autosomal recessive inheritance a recessive allele is realized into a trait only in recessive homozygotes. Recessive diseases in children occur more often in marriages between phenotypically normal heterozygous parents. In heterozygous parents (Ah X Aa) probability of having sick children ( ahh) will be 25%, the same percentage (25%) will be healthy (AA), the remaining 50% (Ah) will also be healthy, but will be heterozygous carriers of the recessive allele. In a pedigree with autosomal recessive inheritance, the disease can manifest itself after one or several generations (Fig. 15.3). It is interesting to note that the frequency of recessive offspring increases significantly in consanguineous marriages, since the concentration of heterozygous carriage in relatives significantly exceeds that in the general population.

Rice. 15.3. Autosomal recessive mode of inheritance

Sex-linked inheritance characterized, as a rule, by unequal frequency of occurrence of the trait in men and women and depends on the localization of the corresponding gene in X- or Y chromosome. Let us recall (see paragraph 13.1) that in the!- and U-chromosomes of humans there are homologous regions containing paired genes (see Fig. 13.4). Genes located in homologous regions are inherited in the same way as any other genes located on autosomes. In the non-homologous region of the Y chromosome there is a gene that determines the differentiation of the male sex, and a number of other genes. They are passed on from father to son and appear only in men (holandric type of inheritance). The % chromosome has two non-homologous regions containing about 150 genes that do not have alleles on the Y chromosome. Therefore, the probability of manifestation of a recessive allele in boys is higher than in girls. Based on genes located on the sex chromosomes, a woman can be homozygous or heterozygous.

A man who has only one Z chromosome will be hemizygous for genes that do not have alleles on the Y chromosome. Inheritance linked to the ^ chromosome can be dominant and recessive (usually recessive). Let's consider A-linked recessive inheritance using the example of a human disease such as hemophilia (blood clotting disorder). An example known to the whole world: the carrier of hemophilia, Queen Victoria, was heterozygous and passed on the mutant gene to her son Leopold and two daughters. This disease penetrated a number of royal houses in Europe and came to Russia (Fig. 15.4). In table 15.1 shows the different types of inheritance.

Rice. 15.4. Pedigree with ^-linked recessive hemophilia A in European royal houses

Types of inheritance of some human characteristics

Table 15.1

Autosomal inheritance
	Dominant	Recessive
	Brown, light brown or green	Gray or blue
	Long eyelashes	Short eyelashes
	Humped nose	Straight or concave bridge of the nose
	Narrow bridge of the nose	Wide bridge of nose
	The tip of the nose looks straight	Snub nose
	Wide nostrils	Narrow nostrils
	Loose lobe	fused lobe

	Full lips	Thin lips
	Dimple on the chin	Smooth chin
	Prominent cheekbones
	Protruding teeth and jaws
	Thick lower lip

End

Autosomal inheritance
	Dominant	Recessive

	Curly
	Excessive body hair	Little body hair
	Premature graying
	Dark skin	Light skin

	Freckles	No freckles
	Right-handedness	Left-handedness
	Six or seven finger hand	Five finger hand
Interlocked with A- chromosome inheritance
	Normal color vision	Colorblindness
Clotting	Normal blood clotting	Hemophilia
Interlocked withY- chromosome inheritance
Genes that determine male development

Introduction

Human genetics and such fundamental disciplines as anatomy, physiology, and biochemistry form the basis of modern medicine. The place of genetics among the biological sciences and the special interest in it are determined by the fact that it studies the basic properties of organisms, namely heredity and variability.

Heredity and variability in humans are the subject of the study of human genetics at all levels of its organization: molecular, cellular, organismal, population. Human genetics owes its successes to a large extent to medical genetics - a science that studies the role of heredity in human pathology. The applied branch of medical genetics is clinical genetics, which uses advances in medical genetics, human genetics, and general genetics to solve clinical problems that arise in humans.

Genetics is one of the most complex disciplines of modern natural science. To understand it deeply, in my work I will consider the main stages of the development of genetics, types of genetics, achievements of genetics in modern medicine, etc.

1. History of the development of genetics

Genetics is a science that studies the patterns of heredity and variability, as well as the biological mechanisms that provide them.

The first scientific step in the study of heredity was taken by the Austrian monk Gregor Mendel, who in 1866 published the article “Experiments on Plant Hybrids,” which laid the foundations of modern genetics.

Before Mendel's discoveries, the theory of so-called fused heredity was recognized. The essence of this theory was that during fertilization, the male and female “beginnings” were mixed, “like colors in a glass of water,” giving rise to a new organism. Mendel showed that hereditary inclinations do not mix, but are transmitted from parents to descendants in the form of discrete (separate) units. These units, presented in pairs (alleles) in individuals, remain discrete and are transmitted to subsequent generations in male and female gametes, each of which contains one unit from each pair. In 1909, the Danish botanist-breeder V. Johansen called them “genes,” and in 1912, the American geneticist T. G. Morgan showed that they are located in chromosomes.

The official date of birth of geneticists is considered to be 1900. Then the data of G. de Vries, K. Correns and K. Chermak were published, who rediscovered the patterns of inheritance of traits established by G. Mendel. The first decades of the 20th century turned out to be fruitful in the development of the basic principles and directions of genetics. The idea of mutations, populations and pure lines of organisms, the chromosomal theory of heredity was formulated, the law of homological series was discovered, data on the occurrence of hereditary changes under the influence of X-rays were obtained, and the development of the foundations of the genetics of populations of organisms began.

In 1953, an international scientific journal published an article by biologists James Watson and Francis Crick on the structure of deoxyribonucleic acid - DNA.

The structure of DNA turned out to be completely unusual: its molecules are enormous in length on a molecular scale and consist of two strands woven together into a double helix. Each of the threads can be compared to a long string of beads. In proteins, the “beads” are twenty different types of amino acids. DNA has only four types of "beads", and they are called nucleotides. The “beads” of the two strands of the DNA double helix are interconnected and strictly correspond to each other. In DNA, opposite the nucleotide adenine is thymine, opposite cytosine is guanine. With this construction of a double helix, each of the chains contains information about the structure of the other. Knowing the structure of one chain, you can always restore another.

The result is two double helices - exact copies of their predecessor. This ability to accurately copy itself is key to life on Earth.

2. Genetics and medicine

2.1 Research methods

In genetics, the main research method is genetic analysis, which is carried out at all levels of the organization of living things (from molecular to population). Depending on the purpose of the study, it is “modified” into particular methods - hybridological, population, mutational, recombination, cytogenetic, etc.

The hybridological method makes it possible to establish patterns of inheritance of individual characteristics and properties of an organism by conducting a series of direct or backcrosses over a number of generations. The patterns of inheritance of traits and properties in humans are established using the genealogical method (analysis of pedigrees). The laws of inheritance of a trait in populations are determined using the population method, or population analysis.

The cytogenetic method, which combines the principles of cytological and genetic analysis, is used in the study of patterns of material continuity in generations of individual cells and organisms and the “anatomy” of material carriers of heredity.

Phenogenetic analysis allows us to study the action of a gene and the manifestation of genes in the individual development of an organism. For this purpose, techniques such as transplantation of genetically different tissues, cell nuclei or individual genes from one cell to another are used, as well as the study of chimeras - experimentally obtained multicellular organisms consisting of genetically different cells, originally belonging to different individuals.

Mutation and recombination analysis are used to study the fine organization and function of genetic material, the structure of various DNAs, their changes, mechanisms of functioning and gene exchange during crossing. The method of molecular genetic analysis is being intensively developed.

2.2 Medical interest

With the development of genetics, it became possible to use its methods in the study of previously incurable diseases, pathologies, etc. Which began to attract considerable interest from scientists working in the field of medicine. Several thousand genetic diseases are known, which are almost 100% dependent on the genotype of the individual. The most terrible of them include: acid fibrosis of the pancreas, phenylketonuria, galactosemia, various forms of cretinism, hemoglobinopathies, as well as Down, Turner, and Klinefelter syndromes. In addition, there are diseases that depend on both the genotype and the environment: coronary disease, diabetes mellitus, rheumatoid diseases, gastric and duodenal ulcers, many oncological diseases, schizophrenia and other mental diseases.

Historically, medical interest in genetics was initially formed in connection with observations of inherited pathological (painful) traits. In the second half of the 19th century, the English biologist F. Galton identified “human heredity” as an independent subject of study. He also proposed a number of special methods of genetic analysis: genealogical, twin, statistical. The study of patterns of inheritance of normal and pathological traits still occupies a leading place in human genetics.

2.3 Human genetics

Human genetics is a special branch of genetics that studies the inheritance of traits in humans, hereditary diseases (medical genetics), and the genetic structure of human populations. Of the areas of human genetics, the most intensively developing are cytogenetics, biochemical genetics, immunogenetics, genetics of higher nervous activity, and physiological genetics.

Human genetics is the theoretical basis of modern medicine and modern healthcare. It is divided into anthropogenetics, which studies the patterns of heredity and variability of normal characteristics of the human body, demographic genetics (population genetics), environmental genetics (the study of the genetic aspects of human relationships with the environment) and medical genetics, which studies hereditary pathologies (diseases, defects, deformities and etc.).

The most important field of human genetics is medical genetics. Medical genetics helps to understand the interaction of biological and environmental factors in human pathology. Sometimes it is considered not as a branch of human genetics, but as an independent field of general genetics.

2.4 Medical genetics

Medical genetics studies the phenomena of heredity and variability in various human populations, features of the manifestation and development of normal (physical, creative, intellectual abilities) and pathological characteristics, the dependence of diseases on genetic predetermination and environmental conditions, including social living conditions. He also develops systems for diagnosis, treatment, prevention and rehabilitation of patients with hereditary diseases and medical examination of their families, studies the role and mechanisms of hereditary predisposition in human diseases.

The formation of medical genetics began in the 30s. XX century, when facts began to appear confirming that the inheritance of traits in humans is subject to the same laws as in other living organisms.

The task of medical genetics is to identify, study, prevent and treat hereditary diseases, as well as to develop ways to prevent the impact of environmental factors on human heredity.

The main branch of medical genetics is clinical genetics, which studies the etiology and pathogenesis of hereditary diseases, the variability of clinical manifestations and the course of hereditary pathology and diseases characterized by hereditary predisposition, depending on the influence of genetic and environmental factors, and also develops methods of diagnosis, treatment and prevention these diseases. Clinical genetics includes neurogenetics, dermatogenetics (studying hereditary skin diseases - genodermatoses), ophthalmogenetics, pharmacogenetics (studying hereditarily determined reactions of the body to drugs). Medical genetics is associated with all sections of modern clinical medicine and other areas of medicine and healthcare, including biochemistry, physiology, morphology, general pathology, and immunology.

Subject and tasks of human genetics. Human genetics, or medical genetics, studies the phenomena of heredity and variability in various human populations, features of the manifestation and development of normal (physical, creative, intellectual abilities) and pathological characteristics, the dependence of diseases on genetic predetermination and environmental conditions, including social conditions life. The formation of medical genetics began in the 30s. XX century, when facts began to appear confirming that the inheritance of traits in humans is subject to the same laws as in other living organisms.

The task of medical genetics is to identify, study, prevent and treat hereditary diseases, as well as to develop ways to prevent the harmful effects of environmental factors on human heredity.

Methods for studying human heredity. When studying human heredity and variability, the following methods are used: genealogical, twin, cytogenetic, biochemical, dermatoglyphic, somatic cell hybridization, modeling, etc.

The genealogical method allows you to find out family ties and trace the inheritance of normal or pathological characteristics among close and distant relatives in a given family based on the compilation of a pedigree - genealogy. If there are pedigrees, then, using summary data for several families, it is possible to determine the type of inheritance of a trait - dominant or recessive, sex-linked or autosomal, as well as its monogenic or polygenic nature. The genealogical method has proven the inheritance of many diseases, such as diabetes, schizophrenia, hemophilia, etc.

It is known that human twins are identical (monozygotic) and fraternal (dizygotic). Identical, or identical, twins develop from one egg fertilized by one sperm. They are always the same sex and are strikingly similar to each other, since they have the same genotype. In addition, they have the same blood type, the same fingerprints and handwriting, even their parents confuse them and cannot distinguish them by the smell of the dog. Only identical twins are 100% successful in organ transplantation, since they have the same set of proteins and the transplanted tissue is not rejected. The proportion of identical twins in humans is about 35-38% of the total number.

The study of identical twins throughout their lives, especially if they live in different socio-economic and climatic conditions, is interesting because the differences between them in the development of physical and mental properties are explained not by different genotypes, but by the influence of environmental conditions.

The cytogenetic method is based on microscopic examination of the structure of chromosomes in healthy and sick people. Cytogenetic control is used in the diagnosis of a number of hereditary diseases associated with aneuploidy and various chromosomal rearrangements. It also makes it possible to study tissue aging based on studies of the age-related dynamics of cell structure, to establish the mutagenic effect of environmental factors on humans, etc.

In recent years, the cytogenetic method has gained great importance in connection with the possibilities of human genetic analysis, which were opened by the hybridization of somatic cells in culture. Obtaining interspecific hybrids of cells (for example, human and mouse) allows one to significantly approach the solution of problems associated with the impossibility of directed crosses, localize a gene on a specific chromosome, establish a linkage group for a number of traits, etc. Combining the genealogical method with the cytogenetic method, and Also, with the latest methods of genetic engineering, the process of mapping genes in humans has significantly accelerated.

Biochemical methods for studying human heredity help to detect a number of metabolic diseases (carbohydrate, amino acid, lipid, etc.) using, for example, the study of biological fluids (blood, urine, amniotic fluid) through qualitative or quantitative analysis. The cause of these diseases is a change in the activity of certain enzymes.

Like any other discipline, modern human genetics uses methods of related sciences: physiology, molecular biology, genetic engineering, biological and mathematical modeling, etc. A significant place in solving the problems of medical genetics is occupied by the ontogenetic method, which allows us to consider the development of normal and pathological characteristics during the individual development of the organism.

Hereditary human diseases, their treatment and prevention. To date, more than 2 thousand hereditary human diseases have been registered, most of them associated with mental disorders. According to the World Health Organization, thanks to the use of new diagnostic methods, an average of three new hereditary diseases are registered annually, which are encountered in the practice of a doctor of any specialty: therapist, surgeon, neurologist, obstetrician-gynecologist, pediatrician, endocrinologist, etc. Diseases that do not have absolutely nothing to do with heredity, practically non-existent. The course of various diseases (viral, bacterial, mycoses and even injuries) and recovery from them to one degree or another depend on the hereditary immunological, physiological, behavioral and mental characteristics of the individual.

Conventionally, hereditary diseases can be divided into three large groups: metabolic diseases, molecular diseases, which are usually caused by gene mutations, and chromosomal diseases.

Gene mutations and metabolic disorders. Gene mutations can result in increased or decreased activity of certain enzymes, or even their absence. Phenotypically, such mutations manifest themselves as hereditary metabolic diseases, which are determined by the absence or excess of the product of the corresponding biochemical reaction.

Gene mutations are classified according to their phenotypic manifestation, i.e., as diseases associated with disorders of amino acid, carbohydrate, lipid, mineral metabolism, and nucleic acid metabolism.

An example of a disorder of amino acid metabolism is albinism, a relatively harmless disease found in Western European countries with a frequency of 1:25,000. The cause of the disease is a defect in the enzyme tyrosinase, which blocks the conversion of tyrosine to melanin. Albinos have milky skin, very light hair, and no pigment in the iris. They have increased sensitivity to sunlight, which causes inflammatory skin diseases in them.

One of the most common diseases of carbohydrate metabolism is diabetes mellitus. This disease is associated with a deficiency of the hormone insulin, which leads to disruption of glycogen formation and increased blood glucose levels.

Chromosomal diseases. This type of hereditary disease is associated with changes in the number or structure of chromosomes. The frequency of chromosomal abnormalities in newborns ranges from 0.6 to 1%, and at the stage of 8-12 weeks about 3% of embryos have them. Among spontaneous miscarriages, the frequency of chromosomal abnormalities is approximately 30%, and in the early stages (up to two months) - 50% and higher.

All types of chromosomal and genomic mutations have been described in humans, including aneuploidy, which can be of two types - monosomy and polysomy. Monosomy is particularly severe.

Whole-organism monosomy has been described for the X chromosome. This is Shereshevsky-Turner syndrome (44+X), which manifests itself in women who are characterized by pathological changes in physique (short stature, short neck), disturbances in the development of the reproductive system (absence of most female secondary sexual characteristics), and mental limitations. The frequency of occurrence of this anomaly is 1: 4000-5000.

Trisomic women (44+XXX), as a rule, are distinguished by disorders of sexual, physical and mental development, although in some patients these signs may not appear. There are known cases of fertility in such women. The frequency of the syndrome is 1:1000.

Men with Klinefelter syndrome (44+XXY) are characterized by impaired development and activity of the gonads, a eunuchoid body type (narrower than the pelvis, shoulders, female-type hair growth and fat deposition on the body, elongated arms and legs compared to the body). Hence the higher growth. These signs, combined with some mental retardation, appear in a relatively normal boy from the moment of puberty.

Klinefelter syndrome is observed with polysomy not only on the X chromosome (XXX XXXY, XXXXY), but also on the Y chromosome (XYY. XXYY. XXYYY). The frequency of the syndrome is 1:1000.

Among the autosomal diseases, trisomy 21, or Down syndrome, is the most studied. According to various authors, the frequency of births of children with Down syndrome is 1:500-700 newborns, and over the past decades the frequency of trisomy-21 has increased.

Typical signs of patients with Down syndrome: a small nose with a wide flat bridge, slanted eyes with an epicanthus - an overhanging fold over the upper eyelid, deformed small ears, a half-open mouth, short stature, mental retardation. About half of the patients have heart and large vessel defects.

Here we consider only a few examples of human genetic and chromosomal diseases, which, however, give a certain idea of the complexity and fragility of its genetic organization.

The main way to prevent hereditary diseases is their prevention. For this purpose, in many countries of the world, including Belarus, there is a network of institutions providing medical and genetic counseling to the population. First of all, its services should be used by persons entering into marriage who have genetically disadvantaged relatives.

The task of medical genetics is to identify, study, prevent and treat hereditary diseases, as well as to develop ways to prevent the harmful effects of environmental factors on human heredity.

Like any other discipline, modern human genetics uses methods of related sciences: physiology, molecular biology, genetic engineering, biological and mathematical modeling, etc. A significant place in solving the problems of medical genetics is occupied by the ontogenetic method, which allows us to consider the development of normal and pathological characteristics during the individual development of the organism.

Conventionally, hereditary diseases can be divided into three large groups: metabolic diseases, molecular diseases, which are usually caused by gene mutations, and chromosomal diseases.

All types of chromosomal and genomic mutations have been described in humans, including aneuploidy, which can be of two types - monosomy and polysomy. Monosomy is particularly severe.

Klinefelter syndrome is observed with polysomy not only on the X chromosome (XXX XXXY, XXXXY), but also on the Y chromosome (XYY. XXYY. XXYYY). The frequency of the syndrome is 1:1000.

Here we consider only a few examples of human genetic and chromosomal diseases, which, however, give a certain idea of the complexity and fragility of its genetic organization.