Presentation on the topic "human genetics". Presentation on the topic "genetics" Ready-made presentations on the topic of genetics

Pimenov A.V.

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Features of the study of human genetics

Currently, the main object of genetic research is the human being. For genetic research, a person is a very inconvenient object for a number of reasons:

• a person has a large number of chromosomes;
• experimental crossing is impossible;
• puberty comes late;
• a small number of descendants in each family;
• equalization of living conditions for offspring is impossible.

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genealogical method

However, despite these difficulties, human genetics is well understood. This was made possible through the use of a variety of research methods.

genealogical method. The use of this method is possible only in the case when direct relatives are known - the ancestors of the owner of the hereditary trait (proband) on the maternal and paternal lines in a number of generations or the descendants of the proband also in several generations. A proband is a person who begins the genetic examination of the family and the compilation of the pedigree.

When compiling pedigrees in genetics, a certain system of notation is used. After compiling the pedigree, its analysis is carried out in order to establish the nature of the inheritance of the trait under study.

• Man;
• Female;
• Gender not clear;
• The owner of the trait under study;
• Heterozygous carrier of the studied recessive gene;
• Marriage;
• Marriage of a man with two women;
• family marriage;
• Parents, children and the order of their birth;
• fraternal twins;
• Identical twins.

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genealogical method

A number of traits are inherited sex-linked:

• X-linked recessive inheritance - hemophilia, color blindness; X-linked dominant inheritance - dark tooth enamel.
• Y-linked - hypertrichosis (increased hairiness of the auricle), membranes between the fingers.

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genealogical method

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genealogical method

Determine if this trait is dominant or recessive?

Sick in every generation, a sick child only in sick parents - so this is a dominant gene.

Is this trait linked to sex chromosomes or autosomes?

With autosomes, since both men and women are equally affected.

Determine the genotypes of individuals for this trait (homozygosity, heterozygosity). Explain your reasoning.

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genealogical method

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genealogical method

A striking example of an X-linked recessive type of inheritance is the inheritance of hemophilia in the royal houses of Europe.

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

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genealogical method

• What can be said about the inheritance of this trait?
• Patients in every generation, only men get sick, so this sign is sex-linked.
• Is this trait linked to the X or Y chromosome?
• With the Y-chromosome, in sick men, all sons are sick, the probability of inheritance is 100% (holandric type of inheritance, the gene is located in a non-homologous region of the Y-chromosome).
• What trait is inherited by this type?

Hypertrichosis.

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genealogical method

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genealogical method

The following are inherited in an autosomal dominant manner:

• polydactyly, brachydactyly (short, due to the absence of phalanges on the fingers), the ability to roll the tongue into a tube, freckles, early baldness, brown eyes, wavy hair.

The lack of freckles, blue eyes, straight hair, albinism, red hair, and other traits are inherited as autosomal recessive.

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Albinism is a recessive trait

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What makes it difficult to study human genetics?

A person has a large number of chromosomes, experimental crossing is impossible, puberty comes late, a small number of offspring in each family, it is impossible to equalize living conditions for offspring.

• Who is a proband?
• The person from whom the genetic examination of the family and the compilation of the pedigree begin.
• How to determine by the pedigree whether a given trait is dominant or recessive?
• Sick in every generation, a sick child only in sick parents - so this is a dominant gene.
• Patients are not in every generation, a sick child in healthy parents means this is a recessive gene.
• How to determine by pedigree whether a trait is linked to autosomes or to the X chromosome?
• If the carriers of the trait are equally male and female, then the trait is linked to autosomes.
• If a trait is much more common in males, it is an X-linked recessive trait.

Let's summarize:

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What traits are inherited X-linked recessive?

Hemophilia, color blindness.

What traits are inherited in an X-linked dominant fashion?

Dark tooth enamel.

How to determine the linkage of a trait with the Y chromosome?

If the carriers of the trait are exclusively males, then the trait is linked to the Y chromosome.

What traits are Y-linked inherited?

Hypertrichosis, webbing between the toes.

Autosomal dominant traits include:

Freckles - no freckles; brown eyes - light eyes; straight hair - curly hair; normal pigmentation - albinism; early baldness - the absence of baldness;

Freckles, brown eyes, curly hair, normal pigmentation, early baldness.

Autosomal recessive traits include:

• Polydactyly - normal number of fingers; brachydactyly - normal fingers; the ability to roll the tongue into a tube - the absence of this ability; non-red hair - red hair.
• Normal number of fingers, normal fingers, no ability to roll tongue, red hair.

Let's summarize:

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twin method

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

Monozygotic twins develop from one zygote, which at the stage of crushing was divided into two (or more) parts. Therefore, such twins are genetically identical and always of the same sex.

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twin method

Monozygotic twins are characterized by a high degree of similarity (concordance) in many ways.

According to those traits that are controlled by genes, the similarity persists until old age.

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twin method

Dizygotic twins can be of the same or different sex. Unlike monozygotic twins, dizygotic twins are often characterized by discordance - dissimilarity in many ways.

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twin method

For all the above signs, concordance in monozygotic twins is significantly higher than in dizygotic twins, but it is not absolute. As a rule, the discordance of identical twins occurs as a result of intrauterine development disorders of one of them or under the influence of the external environment, if it was different.

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twin method

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

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

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The cytogenetic method is based on the study of human chromosomes in normal and pathological conditions. Normally, a human karyotype includes 46 chromosomes - 22 pairs of autosomes and two sex chromosomes.

The use of this method made it possible to identify a group of diseases associated either with a change in the number of chromosomes or with changes in their structure.

Cytogenetic method

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Cytogenetic method

• Such diseases are called chromosomal. These include: Klinefelter syndrome, Shereshevsky-Turner syndrome,
• Patients with Klinefelter's syndrome (47, XXY) are always men. They are characterized by underdevelopment of the sex glands, degeneration of the seminiferous tubules, often mental retardation, high growth (due to disproportionately long legs).
• The extra X chromosome condenses into a Barr body. Barr bodies are found in female cells and in cells of patients with Klinefelter's syndrome.

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Cytogenetic method

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Cytogenetic method

Down syndrome is one of the most common chromosomal diseases (1:774). It develops as a result of trisomy on chromosome 21 (47; 21,21,21).

The disease is easily diagnosed, as it has a number of characteristic features: shortened limbs, a small skull, a flat, wide nose, narrow palpebral fissures with an oblique incision, the presence of a fold of the upper eyelid, and mental retardation. Violations of the structure of internal organs are often observed.

The life expectancy of adults with Down syndrome has increased - today the normal life expectancy is over 50 years. Many people with this syndrome marry. Most men with Down syndrome are infertile. At least 50% of women with Down syndrome can have children. 35-50% of children born to mothers with Down syndrome are born with Down syndrome or other abnormalities.

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The older the woman, the greater the frequency of this syndrome among newborns.

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Biochemical method

The method allows you to detect metabolic disorders caused by changes in genes and, as a result, changes in the activity of various enzymes. Hereditary metabolic diseases are divided into diseases of carbohydrate metabolism (diabetes mellitus), amino acid metabolism (phenylketonuria), lipid metabolism (Tay-Sachs disease), minerals, etc.

Phenylketonuria refers to diseases of amino acid metabolism. The conversion of the essential amino acid phenylalanine to tyrosine is blocked, while phenylalanine is converted to phenylpyruvic acid, which is excreted in the urine. The lack of tyrosine causes insufficient formation of melanin. These children have blue eyes, skin and hair are poorly pigmented.

The disease leads to the rapid development of dementia in children. Early diagnosis and diet can stop the development of the disease. Urine gives a positive reaction with Felling's reagent (5% ferric chloride).

Tay-Sachs disease is caused by the accumulation of lipids in nerve cells, resulting in mental retardation, blindness, and muscle weakness.

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Biochemical method

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

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Features of human genetics were performed by a student of 10 "A" class Savintseva Elena

What is genetics? Genetics is a science that studies the laws of heredity and variability of organisms.

Peculiarities of human inheritance and variability Heredity and variability are universal properties of living organisms. The basic laws of genetics are of universal significance and are fully applicable to humans. However, a person as an object of genetic research has its own specific features.

1. The impossibility of selecting individuals and conducting directional crossing. 2. Small number of offspring. 3. Late puberty and rare (25–30 years) generational change. 4. The impossibility of providing the same and controlled conditions for the development of offspring. 5. The human phenotype is seriously influenced not only by biological, but also by social environmental conditions. Peculiarities:

Methods for studying human heredity. 1. Genealogical (The type of inheritance is studied by compiling pedigrees.); 2. Cytogenetic (The chromosome sets of healthy and sick people are studied, as well as the microscopic structure of chromosomes.); 3. Twin (The genotypic and phenotypic features of twins are being studied.); 4. Biochemical (The chemical composition of the intracellular environment, blood, tissue fluid of the body is being studied.);

Variability is the property of an organism to acquire new traits. Types of variability: Non-hereditary (phenotypic, or modification); Hereditary (combinative, mutational) Patterns of variability.

Mutation types. Gene mutations (changes in genes) A ​​change in the arrangement of DNA nucleotides. Loss or insertion of one or more nucleotides. Replacing one nucleotide with another.

Mutation types. Chromosomal mutations (chromosomal rearrangements) Doubling of a section of a chromosome. Loss of a segment of a chromosome. The movement of a segment of one chromosome to another chromosome that is not homologous to it.

Mutation types. Genomic mutations (lead to a change in the number of chromosomes) Loss or appearance of extra chromosomes as a result of a violation of the meiosis process Polyploidy - a multiple increase in the number of chromosomes

Conclusions: The section of genetics that studies heredity and variability in humans is called anthropogenetics or human genetics. Human genetics is the science of genetically determined differences between people. From human genetics, medical genetics stands out, investigating the mechanisms of development of hereditary diseases, the possibilities of their treatment and prevention. At present, a person is well studied morphologically, physiologically, biochemically, which contributes to the consideration of his genetic characteristics.

Thanks for attention!

Founder of genetics Gregor Mendel (Gregor Johann Mendel) () Austrian naturalist, botanist and religious figure, monk, founder of the doctrine of heredity (Mendelism). Using statistical methods to analyze the results of hybridization of pea varieties (), he formulated the patterns of heredity (Gregor Mendel was born on July 22, 1822, Heinzendorf, Austria-Hungary, now Ginchice. He died on January 6, 1884, Brunn, now Brno, Czech Republic. Gregor Mendel (Gregor Johann Mendel) () Austrian naturalist, botanist and religious figure, monk, founder of the theory of heredity (Mendelism). Using statistical methods to analyze the results of hybridization of pea varieties (), formulated the patterns of heredity (Gregor Mendel was born on July 22, 1822, Heinzendorf , Austria-Hungary, now Ginchice Died January 6, 1884, Brunn, now Brno, Czech Republic.

Genealogical method This method allows, using data on members of several related families, to determine the type of inheritance of any trait. This method allows, using data on members of several related families, to determine the type of inheritance of any trait.

Population method Population - genetic studies are to determine the frequency of occurrence of genes and genotypes in the population. Research allows you to estimate the likelihood of having a child with a certain trait in a given population. Population-genetic studies consist in determining the frequency of occurrence of genes and genotypes in a population. Research allows you to estimate the likelihood of having a child with a certain trait in a given population.

(Marfan's disease, Marfan syndrome, arachnodactyly, dolichostenomelia) is a disease from the group of hereditary collagenopathies, human connective tissue diseases. Hereditary disease, included under the number in the McKusick tabulation system OMIM. The disease has multiple organ manifestations. In addition to characteristic changes in the organs of the musculoskeletal system (elongated bones of the skeleton, hypermobility of the joints), pathology is observed in the organs of vision and the cardiovascular system, which constitutes the classic triad. (Marfan's disease, Marfan syndrome, arachnodactyly, dolichostenomelia) is a disease from the group of hereditary collagenopathies, human connective tissue diseases. Hereditary disease, included under the number in the McKusick tabulation system OMIM. The disease has multiple organ manifestations. In addition to characteristic changes in the organs of the musculoskeletal system (elongated bones of the skeleton, hypermobility of the joints), pathology is observed in the organs of vision and the cardiovascular system, which constitutes the classic triad. Marfan syndrome

Phenylketonuria (phenylpyruvic oligophrenia) A hereditary disease of the group of fermentopathies associated with impaired metabolism of amino acids, mainly phenylalanine. Accompanied by the accumulation of phenylalanine and its toxic products, which leads to severe damage to the central nervous system, manifested, in particular, in the form of mental retardation. (phenylpyruvic oligophrenia) A hereditary disease of the group of fermentopathies associated with impaired metabolism of amino acids, mainly phenylalanine. Accompanied by the accumulation of phenylalanine and its toxic products, which leads to severe damage to the central nervous system, manifested, in particular, in the form of a mental disorder. Phenylalanine

Albinism (from Latin albus white), lack of normal pigmentation: in animals and humans, the skin, hair, iris, in plants, the green color of the whole plant or individual parts (variegation). A. a hereditary trait that depends on the presence of a recessive, i.e., suppressed, gene that blocks the synthesis of pigments in the homozygous state (see Homozygosity) (chlorophyll in plants, melanin in animals). (from lat. albus white), lack of normal pigmentation: in animals and humans, skin, hair, iris, in plants the green color of the whole plant or individual parts (variegation). A. a hereditary trait that depends on the presence of a recessive, i.e., suppressed, gene that blocks the synthesis of pigments in a homozygous state (see Homozygosity) (in plants of chlorophyll, in animals of melanin).

Down syndrome (trisomy on chromosome 21) is one of the forms of genomic pathology, in which the karyotype is most often represented by 47 chromosomes instead of the normal 46, since the chromosomes of the 21st pair, instead of the normal two, are represented by three copies (trisomy, see also Ploidy). There are two more forms of this syndrome: translocation of chromosome 21 to other chromosomes (more often to 15, less often to 14, even less often to 21, 22 and Y-chromosome) 4% of cases, and a mosaic version of the syndrome 5%. (trisomy on chromosome 21) is one of the forms of genomic pathology, in which most often the karyotype is represented by 47 chromosomes instead of the normal 46, since the chromosomes of the 21st pair, instead of the normal two, are represented by three copies (trisomy, see also Ploidy). There are two more forms of this syndrome: translocation of chromosome 21 to other chromosomes (more often to 15, less often to 14, even less often to 21, 22 and the Y chromosome) 4% of cases, and a mosaic variant of the syndrome 5%.

Klinefelter syndrome This is a manifestation of abnormal distribution of chromosomes, in which an additional X chromosome (47,XXY) is added to the normal male (46,XY) set of chromosomes in all or most cells of the body. This is a manifestation of abnormal distribution of chromosomes, in which an additional X chromosome (47,XXY) is added to the normal male (46,XY) set of chromosomes in all or most cells of the body.

"Meow Syndrome" is caused by a deletion of part of the 5th chromosome. Manifestation: dementia develops, the structure of the larynx is disturbed and the voice has a weak timbre. the cause is a deletion of part of the 5th chromosome. Manifestation: dementia develops, the structure of the larynx is disturbed and the voice has a weak timbre.

Medical genetic research Medical genetic consultation consists of 4 stages; diagnosis, prognosis, conclusion, advice. At the same time, frank and friendly communication between the geneticist and the patient's family is necessary. Counseling always begins with a clarification of the diagnosis of a hereditary disease, since an accurate diagnosis is a necessary prerequisite for any consultation. The attending physician, before referring the patient to a medical genetic consultation, should, using the methods available to him, clarify the diagnosis as much as possible and determine the purpose of the consultation. It is also necessary to use genealogical, cytogenetic, biochemical and other special genetic methods (for example, to determine the linkage of genes or use molecular genetic methods, etc.). Medical genetic consultation consists of 4 stages; diagnosis, prognosis, conclusion, advice. At the same time, frank and friendly communication between the geneticist and the patient's family is necessary. Counseling always begins with a clarification of the diagnosis of a hereditary disease, since an accurate diagnosis is a necessary prerequisite for any consultation. The attending physician, before referring the patient to a medical genetic consultation, should, using the methods available to him, clarify the diagnosis as much as possible and determine the purpose of the consultation. It is also necessary to use genealogical, cytogenetic, biochemical and other special genetic methods (for example, to determine the linkage of genes or use molecular genetic methods, etc.).

Conclusion. Genetics Today. The 21st century is the century of genetics ... for a person it is relevant .. because. firstly, many whitenings have a hereditary predisposition .. and knowing which genes, combinations of genes, we can predict certain diseases .. for example, it is already known for sure that essential hypertension in people with a hereditary predisposition has the highest probability of occurrence .. secondly, human genetics is relevant from the point of view of IVF .. we can select any signs for the unborn child .. integrate them into the genome of the egg and get a baby with the signs that we would like to have .. the whole difficulty here is the successful implantation of this egg and further development .. but work is still being done on this .. plus everything .. medical genetic sampling is actively being carried out .. even here in moscow .. in the genetic center .. on a kashirka like .. married couples come there and discuss the possible risk of having a child with certain pathologies ... based on the genealogical method and cytogenetic research. The 21st century is the century of genetics ... for a person it is relevant .. because. firstly, many whitenings have a hereditary predisposition .. and knowing which genes, combinations of genes, we can predict certain diseases .. for example, it is already known for sure that essential hypertension in people with a hereditary predisposition has the highest probability of occurrence .. secondly, human genetics is relevant from the point of view of IVF .. we can select any signs for the unborn child .. integrate them into the genome of the egg and get a baby with the signs that we would like to have .. the whole difficulty here is the successful implantation of this egg and further development .. but work is still being done on this .. plus everything .. medical genetic sampling is actively being carried out .. even here in moscow .. in the genetic center .. on a kashirka like .. married couples come there and discuss the possible risk of having a child with certain pathologies ... based on the genealogical method and cytogenetic research.

Genetics test Which method G. Mendel used: Which method G. Mendel used: Which of the two genes inhibits the action of the other: Which of the two genes inhibits the action of the other: How many types of gametes does a heterozygote form in a monohybrid cross: How many types of gametes does a heterozygote form in a monohybrid cross : How many types of gametes does a homozygote form in dihybrid crossing: How many types of gametes does a homozygote form in dihybrid crossing: If one nucleotide dropped out of the matrix RNA molecule during transcription, then such a mutation refers to: If one nucleotide dropped out of the matrix RNA molecule during transcription, then such a mutation refers to: If the set of sex chromosomes (heterosomes) in the male sex is XY, then such a male sex is: If the set of sex chromosomes (heterosomes) in the male sex is XY, then such a male sex is: human chromosomes: How many genotypes are formed in F2 when monogib in a hybrid cross: How many genotypes are produced in an F2 in a monohybrid cross: How many phenotypes are produced in an F2 in a dihybrid cross: How many phenotypes are produced in an F2 in a dihybrid cross: How many phenotypes are produced in an F1 with incomplete dominance: How many phenotypes are produced in an F1 with incomplete dominance:

Literature A.A. Kamensky, E.A. Kriksunov, VV Pasechnik Biology textbook class. Publisher: Bustard, 2008 A.A. Kamensky, E.A. Kriksunov, VV Pasechnik Biology textbook class. Publisher: Bustard, 2008

Fomina Anna Borisovna

biology teacher

MBOU secondary school No. 6, Kirzhach

Vladimir region

Difficulties in studying human genetics

• The impossibility of free crossing.
• Few offspring.
• Long life cycle.
• Large number of chromosomes.
• Genotypic and phenotypic polymorphism

• Selection of couples appropriate to the study.
• Track the inheritance of traits over several generations.
• Microscopic study of chromosomes, the latest methods of working with DNA.

one). Cytogenetic - analysis of the karyotype in normal and pathological conditions

Methods for studying human genetics

2). Gemini - studies the role of heredity and environment in the development of the human body

Monozygotic

dizygotic

Chang and Eng Bunker are Siamese twins.

Polyembryony is a special type of vegetative reproduction. The embryo is divided into several fragments, each of which independently develops into a full-fledged individual.

Methods for studying human genetics

3). Genealogical - compilation and analysis of pedigrees

• Sets the type of trait inheritance (dominant, recessive, sex-linked).
• Determines the possibility of manifestation of hereditary diseases

Pedigree rules.

1. The pedigree is depicted so that each generation is on its own horizontal line. Generations are numbered in Roman numerals (top to bottom).

2. Drawing up a pedigree begins with proband *.

3. First, next to the proband, place the symbols of his siblings in the order of birth, starting with the eldest (from left to right), connecting them with a graphic yoke.

4. Above the line of the proband, indicate the parents, connecting them to each other with the line of marriage, above the line of the parents, draw the line of grandparents.

5. On the line of parents, depict the symbols of their brothers and sisters with spouses.

6. On the line of the proband, indicate his cousins ​​and sisters, connecting them accordingly with the line of parents. If the proband has nephews, place them on a line below the proband's line.

hereditary diseases

• Congenital(chromosomal)

• Inherited:- genetic; - multifactorial

Deviations due to nondisjunction of chromosomes in humans

47 (in 21 pairs of trisomy

"Cleft palate"

Symptoms

Kline-felter

47 (trisomy in the 15th pair)

Meeting frequency

Shereshevsky-Turner

Genetic diseases

Albinism

Genetic diseases

sickle cell anemia

Multifactorial diseases - with a hereditary predisposition

Mental and nervous diseases

per 1000 people

Schizophrenia

Epilepsy

Affective insanity

Somatic diseases of average age

Bronchial asthma

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A presentation on the topic "Human Genetics" can be downloaded absolutely free of charge on our website. Project subject: Biology. Colorful slides and illustrations will help you keep your classmates or audience interested. To view the content, use the player, or if you want to download the report, click on the appropriate text under the player. The presentation contains 31 slide(s).

Presentation slides

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Features of the study of human genetics

Heredity and variability are universal properties of living organisms. The basic laws of genetics are of universal significance and are fully applicable to humans. However, a person as an object of genetic research has its own specific features. Let us note some of them: 1. The impossibility of selecting individuals and conducting directional crossing. 2. Small number of offspring. 3. Late puberty and rare (25–30 years) generational change. 4. The impossibility of providing the same and controlled conditions for the development of offspring. 5. The human phenotype is seriously influenced not only by biological, but also by social environmental conditions. Conclusion: the study of human heredity requires the use of special research methods.

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Methods for studying human genetics

The genealogical method consists in studying pedigrees based on Mendelian laws of inheritance and helps to establish the nature of the inheritance of a trait, namely autosomal (dominant or recessive) or sex-linked. This is how the inheritance of individual characteristics of a person is established: facial features, height, blood type, mental and mental make-up, as well as some diseases. This method revealed the harmful effects of closely related marriages, which are especially evident when homozygous for the same unfavorable recessive allele. In related marriages, the probability of having children with hereditary diseases and early infant mortality is tens and even hundreds of times higher than the average.

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Autosomal dominant inheritance pattern

Classic examples of dominant inheritance are the ability to roll the tongue into a tube and the "hanging" (loose) earlobe. An alternative to the last sign is a fused lobe - a recessive sign. Another hereditary anomaly in humans, caused by an autosomal dominant gene, is polydactylism, or polydactyly. It has been known since ancient times. In Raphael's painting "The Sistine Madonna" to the left of Mary is Pope Sixtus II, on his left hand he has 5 fingers, and on his right - 6. Hence his name: sixtus is six. Another similar feature, due to dominant genes, is the “Habsburg lip”. People with this trait have a protruding lower lip and a narrow, protruding lower jaw, and their mouth remains half open at all times. The name of the trait is due to the fact that it was often found among representatives of the Habsburg dynasty.

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Autosomal recessive inheritance pattern

In humans, a lot of non-sex-linked traits have been described that are inherited as recessive. For example, blue eyes appear in people who are homozygous for the corresponding allele. The birth of a blue-eyed child from parents with brown eyes repeats the situation of analyzing crossing - in this case it is clear that they are heterozygous, i.e. carry both alleles, of which only the dominant one appears outwardly. The sign of red hair, which also determines the nature of skin pigmentation, is also recessive in relation to non-red hair and appears only in the homozygous state.

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Sex-linked traits

Traits whose genes are located on the X chromosome can also be dominant or recessive. However, heterozygosity for such traits is possible only in women. If any recessive trait is present in a woman only in one of the two X chromosomes, then its manifestation will be suppressed by the action of the dominant allele of the second. In men, in whose cells there is only one X chromosome, all the signs associated with it will inevitably appear. Hemophilia (blood incoagulability) is a well-known disease linked to the X chromosome. The hemophilia gene is recessive in relation to the normal gene, so this disease (homozygosity for this trait) is extremely rare in them. Men who receive the hemophilia gene from a healthy carrier mother develop the disease.

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Biochemical method - a method for detecting changes in the biochemical parameters of the body associated with a change in the genome. Biochemical microanalysis can detect a violation in a single cell. Thus, it is possible to establish a diagnosis in an unborn child by individual cells in the amniotic fluid of a pregnant woman for diseases such as diabetes mellitus, phenylketonuria, etc.

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The twin method is a method of studying twins. Identical (identical) twins: Have the same genotype Differences arise due to the influence of the environment Makes it possible to determine how the environment affects the manifestation of certain traits non-twin siblings Used to compare the expression of a trait in identical and non-identical twins

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The cytogenetic method is a method for studying the structure and number of chromosomes. Allows you to establish visible changes in the chromosomal complex and identify chromosomal mutations. Using this method, it was found that Down's disease and a number of other hereditary diseases are associated with a violation of the number of chromosomes in cells. Chromosomes are studied during the metaphase of mitosis. More often, leukocytes grown in a special medium are used.

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Currently, medicine uses the method of amniocentesis - the study of amniotic fluid cells, which allows you to detect abnormalities in the number and structure of chromosomes in the fetus as early as the 16th week of pregnancy. To do this, take a sample of amniotic fluid by puncture of the fetal bladder. The most common of these anomalies are various manifestations of aneuploidy (i.e., a decrease or increase in the number of chromosomes), as well as the appearance of chromosomes with an unusual structure due to disturbances in the process of meiosis. Aneuploidy and chromosomal rearrangements are cytogenetic features of many human diseases.

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These diseases include, in particular, Klinefelter's syndrome, which occurs in one in 400-600 newborn boys. In this disease, the sex chromosomes are represented by the XXY set. Klinefelter's syndrome is manifested in the underdevelopment of primary and secondary sexual characteristics and distortion of body proportions (tall stature and disproportionately long limbs). Another anomaly is Turner's syndrome, which occurs in newborn girls with a frequency of approximately 1:5000. In such patients, 45 chromosomes are present in the cells, since in their karyotype the sex chromosomes are represented not by two, but by only one X chromosome. Numerous anomalies in the structure of the body are also characteristic of such patients. Both of these diseases - Klinefelter's syndrome and Turner's syndrome - are the result of non-disjunction of sex chromosomes during the formation of gametes in parents.

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Chromosomal diseases can also be caused by nondisjunction of autosomes. For the first time, a connection between a change in the chromosome set and sharp deviations from normal development was discovered in the study of Down syndrome (congenital idiocy). People suffering from this disease have a characteristic eye shape, short stature, short and short-fingered arms and legs, anomalies of many internal organs, a specific facial expression, they are characterized by mental retardation. The study of the karyotype of such patients showed the presence of an additional, i.e. third, chromosomes in the 21st pair (the so-called trisomy). The cause of trisomy is associated with nondisjunction of chromosomes during meiosis in women.

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Population-statistical method This method is used to study the genetic structure of human populations or individual families. It allows you to determine the frequency of individual genes in populations. The vast majority of recessive alleles are present in the population in a latent heterozygous state. So, albinos are born with a frequency of 1:20,000, but one out of every 70 inhabitants of European countries is heterozygous for this allele. If the gene is located on the sex chromosome, then a different picture is observed: in men, the frequency of homozygous recessives is quite high. So, in the population of Muscovites in the 1930s. 7% of colorblind males and 0.5% (homozygous recessives) of colorblind females were present.

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Very interesting studies of blood types have been carried out in human populations. There is an assumption that their distribution in various parts of the globe was influenced by plague and smallpox epidemics. The least resistant to the plague were people of the I blood group (00); on the contrary, the smallpox virus most often infects carriers of group II (AA, A0). The plague was especially rampant in countries such as India, Mongolia, China, Egypt, and therefore there was a "culling" of the 0 allele as a result of increased mortality from the plague of people with blood type I. Smallpox epidemics covered mainly India, Arabia, tropical Africa, and after the arrival of Europeans - and America. In countries with malaria, as you already know (Mediterranean, Africa), there is a high frequency of the gene that causes sickle cell anemia.

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There is evidence that Rh negative is less common in populations living in conditions of high prevalence of various infectious diseases, including malaria. And in populations living in highlands and other areas where infections are rare, there is an increased percentage of Rh-negative people. The population method makes it possible to study the genetic structure of human populations, to reveal the relationship between individual populations, and also sheds light on the history of human distribution around the planet.

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Hereditary diseases and their causes

Hereditary diseases can be caused by disorders in individual genes, chromosomes or sets of chromosomes. Chromosomal diseases occur when the structure of chromosomes changes: doubling or loss of a chromosome segment, turning a chromosome segment by 180 °, moving a chromosome segment to a non-homologous chromosome. For the first time, a connection between an abnormal set of chromosomes and sharp deviations from normal development was discovered in the case of Down syndrome. The frequency of chromosomal mutations in humans is high and is the cause of up to 40% of health problems in newborns. In most cases, chromosomal mutations occur in the gametes of the parents. Chemical mutagens and ionizing radiation increase the frequency of chromosomal mutations. In the case of Down syndrome, a correlation was noted between the probability of having sick children and the age of the mother - it increases 10–20 times after 35–40 years.

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In addition to chromosomal disorders, hereditary diseases can be caused by changes in genetic information directly in the genes. The most common gene, or point, mutations associated with a change in the sequence of nucleotides in the DNA molecule. They can go unnoticed in the heterozygous state, for example, Aa, and manifest themselves phenotypically, passing into the homozygous state - aa. X-linked inheritance manifests itself in the absence of the transmission of a gene through the male line: the X chromosome from the father is not passed on to sons, but is passed on to each daughter. For example, hemophilia (blood incoagulability) is inherited as a recessive, X-linked mutation.

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Treatment of hereditary diseases

Effective treatments for hereditary diseases do not yet exist. However, there are methods of treatment that alleviate the condition of patients and improve their well-being. They are based mainly on the compensation of metabolic defects caused by disturbances in the genome. With hereditary metabolic anomalies, the patient is given enzymes that are not formed in the body or products that are not absorbed by the body due to the lack of necessary enzymes are excluded from the diet. In diabetes, insulin is injected into the body. This allows the patient with diabetes to eat normally, but does not eliminate the causes of the disease.

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Can hereditary diseases be prevented?

So far this is not possible. However, early diagnosis allows either to avoid the birth of a sick child, or to start treatment in a timely manner, which in many cases gives positive results. For example, with early treatment of Down's syndrome, 44% of patients survive to the age of 60, in many cases leading an almost normal life. Various methods are used for early diagnosis. Usually, if standard examination methods give reason to assume hereditary disorders in the embryo, the amniocentesis method is used - the analysis of embryonic cells that are always present in the amniotic fluid.

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Ethical issues in genetics

Genetic engineering uses the most important discoveries of molecular genetics to develop new research methods, obtain new genetic data, as well as in practical activities, in particular in medicine. Previously, vaccines were made only from killed or weakened bacteria or viruses. Such vaccines lead to the development of strong immunity, but they also have disadvantages. For example, one cannot be sure that the virus is sufficiently inactivated. There are cases when the vaccine strain of the polio virus due to mutations turned into a dangerous, close to the usual virulent strain. It is safer to vaccinate with pure proteins of the shell of viruses - they cannot multiply, tk. they do not have nucleic acids, but they cause the production of antibodies. They can be obtained by genetic engineering. Such a vaccine against infectious hepatitis (Botkin's disease) has already been created - a dangerous and intractable disease. Work is underway to create pure vaccines against influenza, anthrax and other diseases.

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Sex correction

Sex reassignment operations in our country began to be done about 30 years ago strictly for medical reasons. The disease of hermaphroditism has been known to science for a long time. According to statistics, in our country it is 3-5 cases per 10 thousand newborns. The basis of this pathology are violations in genes and chromosomes. These disorders can be caused by mutagenic factors (environmental pollution, radioactivity, alcohol, smoking, etc.). Sex reassignment surgeries are complex, multi-stage. Examinations last for months, permission for the operation is given by the Ministry of Health - this excludes a change of sex in homosexuals, mentally handicapped people.

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Organ transplant

Organ transplantation from donors is a very complex operation, followed by an equally difficult period of transplant engraftment. Very often the transplant is rejected and the patient dies. Scientists hope that these problems can be solved with the help of cloning.

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Cloning

This is a genetic engineering method in which the descendants are obtained from the somatic cell of the ancestor and therefore have exactly the same genome. On an experimental farm in Scotland, a sheep named Dolly was recently grazed, which was born using the cloning method. The scientists took a nucleus, containing genetic material, from the udder cell of a mother sheep and implanted it into the egg of another sheep, from which its own genetic material had previously been removed. The resulting embryo was implanted into a third sheep, which acted as a surrogate mother. Following the British, American geneticists successfully cloned monkeys. Animal cloning solves many problems in medicine and molecular biology, but at the same time creates many social problems. Almost any technology applicable to mammals is applicable to humans. This means that it is possible to clone a person, i.e. create twins of people from whom at least one healthy cell is obtained.

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Deformities

The development of a new living being occurs in accordance with the genetic code recorded in the DNA, which is contained in the nucleus of every cell in the body. Sometimes, under the influence of environmental factors - radioactive, ultraviolet rays, chemicals - a violation of the genetic code occurs, mutations occur, deviations from the norm. One of the worst examples is the Chernobyl disaster. People exposed to radioactive contamination have an increased level of various pathologies associated with mutations.

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Genetics and forensics

In judicial practice, cases of establishing kinship are known, when children were mixed up in the maternity hospital. Sometimes this concerned children who grew up in foreign families for more than one year. To establish kinship, methods of biological examination are used, which is carried out when the child is 1 year old and the blood system stabilizes. A new method has been developed - gene fingerprinting, which allows analysis at the chromosomal level. In this case, the age of the child does not matter, and the relationship is established with a 100% guarantee. Approximately 2,000 examinations to establish kinship are carried out in Russia every year.

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Test on the topic: "Methods of human genetics"

1. The main difficulties in the study of human heredity are: a) the inapplicability of genetic laws to humans; b) late puberty; c) the impossibility of directed crosses; d) small offspring.

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2. The main way to prevent hereditary diseases is: a) rehabilitation; b) treatment; c) establishing the causes; d) medical genetic counseling. 3. To establish the dominance or recessiveness of a trait, its linkage with other traits or with sex, the method allows: a) cytogenetic; b) genealogical; c) biochemical; d) twin.

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4. The cytogenetic method allows: a) to establish the nature of inheritance of different genes; b) to study hereditary metabolic disorders; c) to diagnose hereditary diseases caused by chromosomal mutations; d) identify the phenotypic manifestation of signs, due to environmental conditions. 5. The method used to study the role of the environment in the formation of various mental and physical qualities in a person: a) cytogenetic; b) genealogical; c) biochemical; d) twin.

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6. As a result of a change in the sequence of nucleotides in a DNA molecule, there are: a) gene mutations; b) chromosomal mutations; c) somatic mutations; d) various modifications. 7. With the population-statistical method of studying the heredity of a person, they investigate: a) the genealogy of the family; b) distribution of the trait in a large population of people; c) chromosome set and individual chromosomes; d) development of signs in twins.

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