We study the pedigree and learn how to compose it. Learning to draw a family tree and draw a family tree Genealogical tree genetics

It is not necessary to consider this need only from the point of view of controlling the hereditary transmission of diseases, certain issues of kinship and family ties. Pedigree allows you to keep the memory of the ancestors, which in itself is worthy of attention.

In the old days, especially in aristocratic dynasties, it was customary to depict the genealogy in the form of a "tree of generations", where side branches and twigs departed from the ancestral trunk.

Modern symbolism is outwardly much more schematic, but has greater constructive flexibility.

Meanwhile, the basic principle of graphic representation of family ties remained the same, such a schematic genealogy can rightly be called a family tree.

Various ways of graphic representation of pedigrees are allowed: arrangement along a circle of a certain radius or a vertical-horizontal image.

When compiling a pedigree, the following rules must be observed:

The image should be positioned so that each generation is on its own horizontal line. Extensive pedigrees are compiled in a circle.
Persons of the same generation, whether related or not, are located on the same horizontal or one radius. Sibs are located from left to right.
When combined, the lines of mother and father can be depicted below the line of relatives; if they are healthy and do not affect the disease, they may not be recorded in pedigrees at all.
Spouses of relatives of the proband may be depicted below the line of relatives, if they are healthy and do not affect this disease, they may not be recorded in pedigrees at all.
In the case when there are several hereditary diseases in the family that are not related to each other, it is advisable to opt for one.

So, in order to correctly depict your pedigree, you must use the signs given here, denoting male and female (square and circle, but sometimes they use the symbols of Mars and Venus - ♂ and ♀).

Husband and wife are connected by a horizontal line. From the middle of this line, a vertical (descending) connection descends to the descendants of the next generation - the children of this married couple.
Siblings are joined by a linking square bracket.

Thus, it is possible to continue building a pedigree both descending (to descendants), and ascending (to ancestors), and along lateral (family ties) lines.

It is best to draw a family tree on a fairly large sheet of paper ruled horizontally: horizontal lines will help to depict even distant relatives belonging to the same generation (siblings, cousins and second cousins) on the same level.

In principle, you can start a pedigree with yourself or any other relative.

To make the pedigree more compact, it is not necessary to draw all marital relationships in side and descending branches. It is possible to lead connecting lines to children directly from one of the parents.

Individual characters can be signed with initials. If you need more detailed information about the members of the pedigree, then you should not clutter up the drawing with an abundance of inscriptions that will certainly get mixed up. In this case, it is more convenient to designate generations with Roman numerals, and individuals in each generation with Arabic numerals, as is done in our figure.

Then each member of the pedigree will have its own individual number of one Roman and one Arabic numeral. And the most detailed explanations of the pedigree, which are called legends, can be written on separate cards. With a short training, drawing a beautiful and accurate pedigree will not be difficult.

The specificity of a person as a genetic object is reflected in the set of methods that are used in human genetics.

Comes in first place genealogical method , or the pedigree method, which involves tracing a disease or pathological trait in a family or genus, indicating the type of family ties between members of the pedigree. This is one of the oldest and most widely used methods. The method is applicable if the direct relatives of the owner of the studied trait on the maternal and paternal lines in a number of generations are known. Data collection starts from proband, which is the name of the person who first came into the field of view of the researcher. Usually this is a sick person or a carrier of some kind of mutation. Children of the same parent couple (brothers and sisters) are called siblings. The method is used in establishing the hereditary nature of the trait under study, in determining the type of inheritance, the presence of linkage, in medical genetic counseling, etc.

Rules for compiling pedigrees

1. The pedigree is depicted so that each generation is on its own horizontal line or radius (for extensive pedigrees). Generations are numbered in Roman numerals, and members of the pedigree are numbered in Arabic.

2. Drawing up a pedigree starts from the proband. Position the symbol of the proband (depending on gender - a square or a circle marked with an arrow) so that it can be used to draw a pedigree both up and down.

3. First, next to the proband, place the symbols of his siblings in the order of birth (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 a marriage line.

5. On the line (radius) of the parents, draw the symbols of the next of kin and their spouses, connecting their degrees of kinship accordingly.

6. On the line of the proband, indicate his cousins, etc. brothers and sisters, connecting them accordingly with the line of parents.

7. Above the line of parents, draw a line of grandparents.

8. If the proband has children or nephews, place them in a line below the proband.

9. After depicting the pedigree (or simultaneously with it), appropriately show the owners or heterozygous carriers of the trait (most often, heterozygous carriers are determined after the compilation and analysis of the pedigree).

10. Specify, if possible, the genotypes of all members of the pedigree.

11. If there are several unrelated hereditary diseases in the family, make a pedigree of each disease separately.

Pedigree analysis

When analyzing pedigrees, a number of features of different types of trait inheritance should be taken into account. Inheritance types:

ü Autosomal dominant inheritance - inheritance of dominant traits that are not sex-linked. Such signs are found in the pedigree often, in almost all generations, equally often in both sexes; if the carrier is one of the parents, then the trait appears either in all descendants, or in half. Dwarfism, the presence of freckles, six-fingeredness, myopia, etc. are inherited according to this type.

ü Autosomal recessive inheritance - inheritance, in which non-sex-linked traits are phenotypically manifested only in homozygotes for recessive alleles. The sign is rare, not in all generations, equally common in both sexes; the trait can manifest itself in children, even if the parents do not have this trait; if one of the parents is a carrier of the trait, then the trait will either not appear in the children, or will appear in half of the offspring. This is how diabetes mellitus, some forms of schizophrenia, red hair, negative Rh factor, etc. are inherited.

Often, autosomal recessive inheritance of a trait manifests itself in the case of consanguineous marriages.

ü Dominant X-linked inheritance - the trait is more common in females, since they can inherit it with equal probability from both their father and mother, and men can only inherit it from their mothers. If the mother is sick and the father is healthy, then the trait is transmitted to offspring regardless of gender, and can occur in both boys and girls. If the mother is healthy and the father is sick, then all the daughters will show the symptom, but the sons will not. Darkening of tooth enamel, etc.

ü Recessive X-linked inheritance - the symptom is more common in males, usually manifests itself through a generation; if both parents are healthy, but the mother is heterozygous, then the trait often appears in 50% of the sons; if the father is sick and the mother is heterozygous, then females can also become owners of the trait. Hemophilia, color blindness, etc.

ü Y-linked inheritance - the trait occurs only in males; if a father carries a trait, then, as a rule, all his sons have this trait. Hypertrichosis etc.

Mitochondrial or cytoplasmic inheritance – it is the inheritance of genes localized in the DNA of mitochondria. The features of this type of inheritance are determined by the fact that mitochondria in human cells always have a maternal origin, since they enter the zygote only with the cytoplasm of the egg (the sperm head is practically devoid of cytoplasm and cytoplasmic structures). Mitochondrial DNA contains several thousand genes. Mutations of these genes lead to the development of rather severe diseases of the nervous, muscular system and sensory organs, which constitute a special group of human pathology - mitochondrial diseases.
Mitochondrial inheritance is characterized by the following features:The disease is transmitted only from the mother; bboth boys and girls cheer; bAll fathers do not pass diseases on to their daughters or sons.

Mitochondrial diseases include: Leber's optic nerve atrophy, progressive ophthalmoplegia, Zellweger syndrome, Kearns-Sayre syndrome, mitochondrial myopathy, etc.

The purpose of the master class:

teach the technology of compiling a family tree, symbols;
show the sequence of actions, methods and forms of pedagogical activity.

None of us fell off the moon.
We are all branches and leaves of a huge
and intertwined human tree.

Teacher. First you need to give the concept of what is genealogy and family tree?

Genealogy- a section of historical science that studies the origin and connections of individual genera.

Genealogical tree- an image of the history of the genus in the form of a branched tree.

Now let's compose a syncwine for these concepts and see what we get.

To complete the first task, you study in detail the reference, scientific literature, thanks to which you got acquainted with various methods for studying human genetics. Of course, at present, genetics is so developed that the solution of such a problem as the study of traits is not difficult for science. Indeed, scientists have at their disposal a large number of methods of work: clinical and genealogical, twin, biochemical, population, ontogenetic, cytological.

Unfortunately, for people who are not involved in the field of science, it is simply impossible to apply most of even these methods. With all the desire, an ordinary person often does not have the opportunity to purchase expensive equipment. So, for example, to use the cytogenetic method in the work, it is necessary to have the necessary special reagents, which are almost impossible to acquire for an ordinary person. The biochemical method is also impossible to use, since it is quite complicated and expensive.

Having studied these methods of genetic research, I came to the conclusion that the most suitable in your case is the clinical and genealogical method. It is really convenient, because to use it you only need to compile your pedigree, having received information about relatives. Of course, obtaining this information can be difficult, but this problem is much easier to solve with the help of a survey of relatives than to look for equipment for other research methods.

The genealogical method was proposed at the end of the 19th century by F. Galton (cousin of Charles Darwin by their grandfather Erasmus Darwin).

The pedigree designation system was proposed by G.Just in 1931.

Genealogy as knowledge of kinship appeared along with human society and lives at all stages of its development. In modern foreign encyclopedic dictionaries, the article "Genealogy" begins with the biblical Old Testament section. The Bible tells about the origin and kinship of all the numerous peoples. The flourishing of genealogy in many European countries coincides with the development of feudalism. The knowledge of the genealogy of the family was of particular importance in the Middle Ages in connection with the establishment and registration of class (especially noble) privileges. This led to the emergence of special genealogical reference books (in the form of a family tree or tables), which indicated all members of the main and side branches of the genus, their marriage ties. Especially many such reference books appeared in the 15th century, government positions were created that were responsible for the correct compilation of genealogies.

The study of pedigrees, that is, the nature of the distribution of hereditary traits in families, is the main method of genetic research. Since in human genetics, unlike experimental genetics, analytical crosses are not applicable, it is necessary to study the nature of inheritance of a particular trait by collecting family data. The analysis of pedigrees makes it possible to trace the Mendelian splitting of traits, obtain information on allelism and linkage, and study monofactorial inheritance. True, a number of important traits inherent in a person, such as the level of intelligence, for example, are determined by many interacting genes, each of which has only a small effect. But here, too, the main method of studying them is the analysis of intra-family similarity, which is essentially an expanded version of the pedigree method.

One of the stages in the collection of a pedigree is the collection of information about all blood relatives on the maternal and paternal lines. First, everything about the mother of the proband, her siblings and their children is clarified. Then data about the grandmother on the mother's side, her siblings are recorded. If possible, information is collected about the proband's great-grandmother and great-grandfather. Next, information is collected about the proband's maternal grandfather, his siblings, their children, and grandchildren. Only after the final collection of information about relatives on the mother's side, information on relatives on the father's side is collected in a similar way. Father's relatives are depicted in the left half of the pedigree, and attention should be paid to the correct designation of the lines of intersection.

Genealogy can be symbolic (genealogical tree), or in the form of a table. It was the symbolic way of designing the genealogy that I chose.

If the pedigree is very extensive, then all generations are not depicted in horizontal rows, as in most cases, but are arranged in a circle.

If several signs are traced in the pedigree, then non-standard symbols are used to designate each of them.

An explanatory note is attached to the pedigree - a legend, including a list of non-standard designations.

Each generation is depicted on one line and is indicated by Roman numerals from top to bottom. Each member of a generation, including spouses, is designated by an Arabic numeral (numbering from left to right for each generation starting from one).

Reflection. De Greef method.

You need to draw three identical circles on the board. The first circle represents your teacher, the second represents you, and the third represents your neighbour. From each circle, a line must be lowered down. From the one of you who is the most diligent, you need to omit the longest line, from the one who is the most undiligent, the shortest, from the one who is average, the middle one. This technique is used to determine the self-esteem of students. Students evaluate your work, theirs, and their neighbor's.

I think that the result of your work could be the words of the famous English geneticist Kurt Stern, who believed that all people on Earth are related to each other by one degree or another of kinship.

Bibliography:

My ancestry. - Leningrad publishing house, 2008.
Fundamentals of genetics. Clinical and genetic foundations of correctional pedagogy and special psychology. - Moscow, 2003. Authors: E.M. Mastyukova, A.G. Moskovkina.
Human genetics - publishing house "Mir"; Moscow, 1967
Encyclopedic dictionary of a young biologist - publishing house "Pedagogy"; Moscow, 1986 Compiled by: M.E. Aspiz.
General biology: grades 10-11 - Drofa publishing house; Moscow, 2005. Authors: A.A. Kamensky, E.A. Kriksunov, V.V. Pasechnik.

Memo on compiling a family tree

Rule one: the work on the pedigree is endless, it can last a lifetime and will require careful research, so you need to stock up on patience, diligence and accuracy.
Rule two: the branches (roots) of the tree must be absolutely symmetrical, and the number of branches must be even, the number of ancestors doubles with each ascending generation: 2 parents, 4 grandfathers, 8 great-grandfathers, etc.
Rule three: when filling out a pedigree, try to ensure that each branch contains a surname, name, patronymic. Remember the state of health of the relatives indicated in it, the characteristics of the character, the fate of each. Ask everyone who knew them about this. Maybe one of them was a long-liver, and someone died. Put dates of birth and death, and make notes about past illnesses.
Rule four: when describing your family, you try to find out as much as possible about those who are no longer alive, and completely forget about those who are nearby, meanwhile, grandfathers, grandmothers, mothers and fathers can help a lot.
The fifth rule: when collecting information, do not immediately divide the facts into essential and seemingly unimportant to you.
Rule six: do not put off for one day what you plan to work on the pedigree, especially if it concerns older people.
Rule seven: until you can determine the significance of this or that document, material, collect everything that concerns your family.

After carefully collecting data on the pedigree, specifying the necessary information about the patients and examining the necessary family members, you can begin to analyze the pedigree. In this case, it is necessary:

to establish whether this sign or disease is single in the family or there are several cases of this pathology (family character);
identify persons suspicious of this disease, and draw up a plan for their examination and diagnosis;
determine the type of inheritance and find out which line - maternal or paternal - is the transmission of the disease;
identify persons in need of medical genetic counseling, determine the clinical prognosis for the proband and his sick relatives, taking into account the characteristics of the disease and its genetic characteristics;
develop a treatment and prevention plan, taking into account the individual and family characteristics of the disease.

When analyzing a pedigree, a doctor may come across genetic and chromosomal diseases, diseases, in the development of which both genetic and environmental factors are involved, "unknown" diseases.

In this regard, it is necessary to recall the definition of some concepts and terms of genetics, primarily "trait" and "gene". The concept of "sign" is interpreted in genetics widely. It denotes any morphological, physiological, biochemical, pathological and other properties, processes, reactions, in respect of which there are species, population or individual differences between people. Variations in traits are due to both genetic and environmental factors. The term "gene" refers to the elementary unit of heredity that controls the development of a single hereditary trait. Since Mendel's work, the properties of genes have been judged by their action - the transfer of hereditary traits from parents to children. For the convenience of analyzing pedigrees, genes are denoted by letters of the Latin alphabet.

The transmission of traits in a descending series of generations indicates a high stability of genes. However, in some cases, there is a change in the gene, called a gene mutation. When a gene mutates, it becomes its own allele. Alleles are modifications or, in the figurative expression of N. P. Dubinin, "isotopes" of the same gene. Alleles control alternative variations of the same trait. They are usually denoted by the same letter, but in different spellings. For example, having designated the gene of pigmentation with the letter B, the allelic gene for the absence of pigment in hair is designated with the letter b, thereby showing that gene b is the result of a mutation of gene B. If this gene has mutated several times in a population, then a series of modifications of the original gene is formed, consisting of multiple alleles. An example is the J gene, which controls blood types. Its allele J A controls the synthesis of antigen A, the allele J B - antigen B, and the allele J b - the absence of these antigens in erythrocytes. The same applies to genes that cause hereditary diseases. For example, the deafness s gene is an allele of the normal hearing gene S, and the hemophilia h gene is an allele of the normal blood coagulation gene H.

The development of molecular genetics led to the discovery of the fine chemical structure of the gene and the mechanism of its action. Chemically, a gene is part of a giant deoxyribonucleic acid (DNA) molecule. Its main properties: high stability of the structure, the ability to self-reproduce and program the biosynthesis of specific proteins. The primary action of each gene is that it serves as a template for the synthesis of one specific protein. For example, the pigmentation gene B mentioned above is a template for the synthesis of an oxidative enzyme that catalyzes the conversion of a colorless chromogen (tyrosine derivative) into the black pigment melanin. When gene B is mutated, its b allele occurs, which programs the synthesis of an altered protein that does not have enzymatic properties. In people with the b gene, melanin is not formed, their skin and hair remain colorless. Similarly, the H gene programs the synthesis of antihemophilic globulin, a protein necessary for normal blood clotting. The h allele of this gene programs the synthesis of an altered protein, which leads to pathology - hemophilia.

The composition of each gene, along with a site that programs protein biosynthesis (exon), includes a site that performs regulatory functions (intron). The significance of the intron has not yet been fully elucidated. However, it is obvious that it plays a certain role in the expression of the gene, the implementation of its action in the cell.

The progress of cytogenetics has made it possible to study the properties of genes at the cellular level. It has been established that genes are localized in chromosomes and each of them occupies a strictly defined place in it - a locus. Moreover, in this locus there can be only one of the alleles of a certain gene, for example, either B or b, but not other genes that are located either in another locus of the same chromosome, or in another chromosome. Consequently, each chromosome differs from the others not only in shape and structure, but, more importantly, in the blocks of genes localized in it. A complete single set of genes that determine the entire set of hereditary traits is contained in the haploid set of chromosomes and is called the genome. Such a set of genes is present in gametes - sperm and eggs. In a fertilized egg (zygote) and in all somatic cells there is a double set of chromosomes and, consequently, a double set of genes, one of which is obtained through the mother's egg, and the second through the father's sperm. This applies to all genes localized in autosomes (in contrast to the sex chromosome genes, which will be discussed below).

Organisms that have two identical alleles of a given gene in a diploid (double) set (for example, BB or bb) are called homozygous, and with different alleles (Bb), heterozygous. In heterozygotes, alleles can interact in various ways. Usually one of them dominates (predominates) over the other - a recessive allele that does not show its effect in heterozygotes.

Consider the main types of inheritance of monogenic diseases.

Autosomal dominant inheritance pattern

Due to the fact that the dominant genes that determine the development of the disease are usually lethal in the homozygous state, all marriages between sick and healthy family members are of the Aa X aa type, where A is the dominant gene that determines the development of a hereditary disease, and - recessive gene. Pedigree in this case has the following characteristic features.

Each sick family member usually has a sick parent.
The disease is passed from generation to generation; there are patients in every generation.
Healthy parents will have healthy children.
Both men and women can get sick equally, since the gene is localized in the autosome.
The probability of having a sick child if one of the parents is sick is 50%.

On fig. 3 shows the pedigree of a family "affected" by brachydactyly. The anomaly is observed in every generation. From marriages where one of the spouses has shortened fingers, and the second is normal, children are born with an anomaly. This is one of the signs of dominant inheritance. The second sign confirming the dominance of the gene is that there are no children with brachydactyly from marriages in which both parents have a normal hand structure (one marriage in the second generation, four marriages in the third generation). The anomaly is equally present in both men and women.

The above signs are typical only for cases of the "classic" autosomal dominant type of inheritance. However, in practice, cases are not uncommon when carriers of a dominant gene remain phenotypically healthy or their disease is erased. As a result, the type of pedigree changes and gaps in generations appear. In the pedigree of the family shown in Fig. 4, the disease (Huntington's chorea) can be traced in every generation. From marriages in which one of the spouses is sick and the other is healthy, children are born with this anomaly. These are signs of autosomal dominant inheritance. However, in the second generation of marriage between healthy parents, a son with a pathology appears. The suggestion that a similar mutation occurs again in a family is almost unbelievable. This can be explained by the fact that the gene of this disease has incomplete penetrance and one of the relatives (II-3) does not manifest itself ("generation skip"), but he passed this gene on to his son.

Penetrance is the likelihood of a gene being expressed. It is expressed as the percentage of cases of the number of carriers. So, if the dominant gene appears in the phenotype in all its carriers, then its penetrance is 100%, in this case they speak of complete penetrance. If among the carriers of the pathological dominant gene only 50% are ill, then the penetrance is 50%, if 25% - then also 25%.

Carrying a dominant gene without a phenotypic manifestation can be suspected in one of the parents if among his descendants there are persons with the corresponding dominant disease. When healthy parents have a sick child and there are other cases of this disease in the pedigree, it can be assumed that one of the parents of the patient had a pathological gene that did not penetrate, but was passed on to the offspring.

The dominant gene also has another property that makes it difficult to establish an autosomal dominant type of inheritance. This is a different expressiveness. The concept of expressivity is similar to the concept of disease severity. With a very low expression of the gene, it seems that a person is healthy, with a high expression, a severe form of the disease develops. Sometimes, as a result of a thorough study by all available clinical and paraclinical methods, it is possible to make a diagnosis of an erased form of a dominant disease. The diagnosis of an erased form is valid only when pronounced clinical forms of this disease occur in this family. The autosomal dominant Marfan syndrome has extremely variable expressivity. You can meet its very severe forms with a triad of symptoms typical of the syndrome:

damage to the skeletal system (scoliosis, kyphoscoliosis, deformity of the sternum, arachnodactyly, asthenic physique, abnormally high growth);
blurred vision (bilateral dislocation of the lens);
pathology from the cardiovascular system (aortic dilation).

There are also erased clinical forms that are not diagnosed (asthenic physique, scoliosis of the 1st degree, arachnodactyly, slight myopia). Mild clinical forms of the disease can be easily missed, then the pedigree also loses its "classic" appearance: generation gaps appear.

Given this feature of the dominant gene, it is advisable to conduct a personal examination of all family members (especially those suspicious of carrying the gene, based on the genetic situation) using modern diagnostic methods in order not to miss the erased clinical forms of this disease. On fig. 5 shows the pedigree of a family whose members have Marfan syndrome. On fig. 5, and the pedigree is presented only taking into account the pronounced clinical forms, and in fig. 5, b shows cases of the disease with an erased clinical picture.

With an autosomal dominant type of inheritance, sporadic cases can also be observed, i.e., in none of the previous generations, no one suffered from this disease. Such facts can be explained by several reasons: one of the parents of the proband is sick, but in a very mild form. Excluding the first possibility, the most likely explanation is that the disease occurred in this family as a result of a new mutation.

Some genes located on autosomes are more active in either men or women. This is called a predominant lesion of one sex or another. If only one sex is affected, then it is called sex-limited inheritance. Gout and presenile alopecia are examples of an autosomal dominant pattern of inheritance with a predominant lesion of males. Such a selective defeat of men is associated with the action of male sex hormones. Hippocrates first noticed that "eunuchs do not get gout and do not become bald." An example of sex-limited inheritance in which only males are affected is the testicular feminization syndrome, where the female phenotype is formed with a male (46XY) karyotype. The cause of this syndrome is a gene mutation that leads to peripheral tissue resistance to male sex hormones. Although the gene is located on the autosome, only males are affected.

Autosomal recessive inheritance pattern

The main feature of the recessive gene is that it shows its effect only in the homozygous state. Therefore, in a heterozygous state, it can exist in many generations without manifesting itself phenotypically. As a result, the first patient with a recessive disease appears many generations after the mutation occurs (Fig. 6), since the birth of a sick child is possible only if both parents carry the recessive gene for the disease. There are three types of such marriages:

aa X aa - all children are sick;
Aa X aa - 50% of children will be sick (genotype aa), 50% phenotypically healthy (genotype Aa), but will be carriers of the mutant gene;
Aa X Aa - 25% of children will be sick (genotype aa), 75% phenotypically healthy (genotypes AA and Aa), but 50% of them (genotype Aa) will be carriers of the pathological gene.

All three types of marriages are possible only if the recessive gene is often found in the population. Therefore, the frequency of occurrence of an autosomal recessive disease is directly dependent on the prevalence of the mutant gene. The frequency of recessive hereditary diseases is especially increased in isolates and populations in which there are a lot of consanguineous marriages (Fig. 7).

Suppose the frequency of occurrence of a recessive gene in a population is 1:100. Since the probability of meeting heterozygous carriers of the mutant gene in a married couple is equal to the product of frequencies 1:100 1:100 = 1/10,000, and with this type of marriage, the probability of having a sick child is 25% (1/4)> then the incidence of the disease will be 1/ 10,000 1/4 \u003d 1/40,000. However, if cousins \u200b\u200bwhose families have this gene marry, the risk of having a sick child increases 10 times. This is due to the fact that cousin siblings share 1/8 of their genes. Suppose that one of them has a mutant gene, then the probability of having a child with a pathology will be 1/3200 (1/100 gene frequency in populations 1/8 common genes 1/4 probability of having a sick child with an autosomal recessive type of inheritance ).

Based on the fact that the commonality of genes in parents and children, brothers and sisters (except for monozygotic twins), i.e., in relatives of the first degree of kinship, is 50% (1/2), it is possible to calculate the indicators of commonality of genes in relatives of different degrees of kinship (Table 1).

Thus, the probability of having a sick homozygous child in consanguineous families with a recessive gene is much higher than in unrelated marriages, since the "concentration" of heterozygous carriage in them is higher than in the general population. The lower the prevalence of a recessive gene, the more often the corresponding recessive disease occurs among children from consanguineous marriages. The negative impact of such marriages on offspring is also evidenced by the fact that mental retardation among children from these marriages is 4 times higher than in families with unrelated marriages, and amounts to 16%.

So, autosomal recessive inheritance has the following distinctive features.

Sick children are born from healthy parents. The most common type of marriage is a marriage between heterozygous carriers (Aa X Aa), when both parents are phenotypically healthy, but they may have children with a homozygous genotype.
Healthy children are born from a sick parent. When a patient with a recessive disease enters into a marriage with a healthy one (the type of marriage is usually AA X aa), all children will be healthy.
Mostly siblings (brothers, sisters) get sick, and not parents - children, as in the dominant type of inheritance.
The pedigree shows a higher percentage of consanguineous marriages.
All parents of sick children are heterozygous carriers of the pathological gene.
Men and women are equally often ill.
In heterozygous carriers, the ratio of sick and healthy children is 1:3. The probability of the birth of the patient is 25% for each subsequent child. As with dominant inheritance, this ratio applies to families with a large number of children or to the sum of children from many families with the same recessive disease. Theoretically, in a marriage between two heterozygous carriers, in 75% of families with one child this child will be healthy, in 56% of families with two children both children will be healthy, but only 32% of families with 4 children will have all healthy children.

Table 2. The probability of having healthy offspring in the presence of a sick child
Number of sick children	Probability with the number of children in the family
Number of sick children	1	2	3	4
0	3/4	9/16	27/64	81/256
1	1/4	6/16	27/64	108/256
2	-	1/16	9/64	54/256
3	-	-	1/64	12/256
4	-	-	-	1/256

When calculating the frequency of people with a recessive disease, it must be taken into account that a certain number of families will have only healthy children and will not fall into the doctor's field of vision. If this is not taken into account, then the incidence of patients will significantly exceed the expected 25% (Table 2).

As already noted, the most common type of marriage in autosomal recessive inheritance is a marriage between heterozygous carriers. Then all these features will be observed in the pedigrees. However, in some cases, if there is an autosomal recessive disease in the family, the pedigree can "take the form" of a pseudo-dominant type of inheritance. This can be in two cases:

the disease is caused by a frequently occurring recessive gene;
the disease is caused by a rare recessive gene, but the family has a high percentage of consanguineous marriages (Fig. 8).

If the pathology caused by the recessive gene does not affect the viability of the organism and is quite common in the population, then marriages between two persons with an autosomal recessive disease are possible. From a marriage of this type (aa X aa), all children will have this pathological phenotype. For example, from the marriage of two albinos, all children will be albinos (Fig. 9). On the pedigree Fig. 8 shows the inheritance of alkaptonuria, an autosomal recessive disease. Due to the high frequency of related marriages in the family, the type of pedigree resembles that of the dominant type of inheritance (pseudo-dominant type).

With an autosomal recessive type of inheritance, as with an autosomal dominant, different degrees of expressiveness of the trait and the frequency of penetrance are possible.

Most often, recessive diseases occur sporadically in families. In this case, the appearance of a sick child may either be the result of the first marriage in the family between heterozygous parents, or it may occur in the marriage of a heterozygous carrier with a healthy one, in whose germ cell a primary mutation has occurred. In order to correctly assess a sporadic case of a recessive disease to establish the degree of risk of having other sick children, it is necessary to determine the heterozygous carriage. Currently, tests have been developed that can detect subtle phenotypic differences between heterozygous carriers and healthy individuals.

X-linked type of inheritance

Genes located on the X chromosome, as in autosomal inheritance, can be dominant and recessive. The main feature of the X-linked type of inheritance is the lack of transmission of the corresponding gene from father to son, since men, being hemizygous (have only one X chromosome), pass their X chromosome only to their daughters. If a dominant gene is localized on the X chromosome, this type of inheritance is called X-linked dominant. It is characterized by the following features.

If a father is sick, then all his daughters will be sick, and all his sons will be healthy.
Children will be sick only if one of the parents is sick.
Healthy parents will have healthy children.
The disease can be traced in every generation.
If the mother is sick, then the probability of having a sick child is 50%, regardless of gender.
Both men and women are ill, but in general, there are 2 times more sick women in the family than sick men.

Analysis of the pedigree depicted in fig. 10 shows that the trait of brown tooth enamel is inherited in a dominant manner. This is evidenced by the fact that children with brown teeth are born from marriages in which one of the parents is sick and the other is healthy. If both parents have normal tooth coloration, the children also do not have this anomaly (two families from the fourth generation). But the fourth generation attracts attention: out of 12 siblings, 4 have a normal color of teeth, and 8 are brown. The mother of these children had white teeth, while the father had brown teeth. It is important that only the men of this generation inherited the normal color of the enamel, and all the women inherited the defect in the color of the enamel. Why is this gene inherited only by women? It should be assumed that the gene for the brown color of tooth enamel is located on the X chromosome. Only in this case, it could not be in the sons, but it must have got to the daughters. At the same time, he manifested himself in all the daughters. Therefore, it is X-linked dominant inheritance.

When a recessive gene is localized on the X chromosome, the type of inheritance is called ^-linked recessive. This type is characterized by the following.

Predominantly males get sick.
The disease is observed in male relatives of the proband on the maternal side.
A son never inherits a disease from his father.
If the proband is a woman, her father is necessarily sick, and all her sons are also sick.
From the marriage of sick men and healthy women, all children will be healthy, but daughters may have sick sons.
In a marriage between a healthy man and a heterozygous woman, the probability of having a sick child is 50% for boys and 0% for girls.

From the one shown in Fig. 11 pedigree shows that only men get sick. This suggests that the disease gene is sex-linked. Sick children are usually born to healthy parents. Therefore, the gene of the analyzed disease is recessive. At the same time, from the marriages of sick men with healthy women, children, regardless of gender, turn out to be healthy. This is possible when the recessive gene for the disease is located on the X chromosome. In men, there is only one X chromosome and the recessive gene cannot be suppressed, while in women there are two X chromosomes. Therefore, if a woman inherits this X chromosome with the disease gene from her father, then the dominant gene of the norm of another X chromosome, received from the mother, will “suppress” the disease gene.

In some cases, it is difficult to determine the type of inheritance in X-linked recessive inheritance. For example, in the one shown in Fig. 12 pedigree observed male infertility. The disease is transmitted by women who are healthy, but it is not known whether women in the homozygous state of the gene will develop infertility. In this case, an autosomal dominant type of inheritance, limited to the male sex, cannot be excluded.

Genes located in the unpaired region of the Y chromosome, which are not on the X chromosome, are inherited according to the hollandic type - by all the sons of the affected father, and his daughters remain healthy, since they never receive the father's Y chromosome.

Many cases of polymorphism of human traits are due to the action of two (or several) pairs of non-allelic genes, and when certain genes are combined, a qualitatively new trait arises. Among such phenomena, oligogenic-complementary inheritance is of the greatest importance. In this case, the development of a trait is determined by two (or several) alleles from different pairs; for example, the alleles of one pair determine the presence or absence of the enzyme, and the alleles of the other pair determine the presence or absence of the corresponding substrate. A trait develops only when, in a combination of complementary alleles, the allele of one of the pairs determines the presence of the enzyme, and the allele from the other pair determines the presence of the substrate.

In the 1930s and 1950s, it was assumed that most of both normal and pathological human traits are transmitted through one or another of the types of inheritance discussed above. However, the development of methods of medical statistical analysis and an increase in the resolution of genetic and biochemical methods at the turn of the 60-70s led to a revision of the type of inheritance of many traits (especially diseases) in favor of the so-called polygenic inheritance. This, in turn, made it possible to further formulate the concept of the existence of diseases with a hereditary predisposition, which is extremely important for modern medical genetics.

In connection with the importance currently attached to polygenic (multifactorial) inheritance, we will dwell on it in more detail.

Multifactorial inheritance

Often the development of an individual trait is determined by many pairs of genes, the dominant alleles of which, acting on the trait in the same direction, seem to sum up their influence (additive effect). The influence of each gene can be very weak, but their combined effect determines the significant severity of the trait. Polygenic inheritance explains, firstly, the inheritance of quantitative traits (for example, height, body weight, many pharmacokinetic constants), and secondly, qualitative features (for example, peptic ulcer and hypertension, diabetes, schizophrenia). In the latter case, one often speaks of additive polygenic inheritance with a threshold effect: a new qualitative state (disease) is achieved only when the total effect of alleles exceeds a certain “threshold” necessary for the development of a trait.

With regard to diseases with a hereditary predisposition, this means that the alternative distribution of the “sick” - “healthy” phenotypes noted in the population actually reflects the distribution of individuals in the population that is not directly observed by the probability of the disease (by predisposition to it or, as they recently began to say, by "susceptibility"). At the same time, susceptibility, which in the general case can be considered as a quantitative trait, is due to the action of both genetic and environmental factors; their joint influence ultimately determines the manifestation (disease) or non-manifestation (health) of the phenotype [Gindilis V. M., Finogenova S. A., 1978; Falconer D., 1960]. In other words, a pathological phenotype appears when the combined effect of genetic and environmental factors reaches or exceeds a certain susceptibility threshold. At the same time, all individuals with a pathological phenotype (patients) are located on the susceptibility scale above (further) this threshold value, i.e., they fill the "tail" of the population distribution (Fig. 13).

Analyzing the theoretical model depicted in Fig. 13, the following conclusion can be drawn: as with other types of inheritance, the polygenic model also suggests that the likelihood of the disease among relatives of people suffering from diseases with a hereditary predisposition is much higher than in the general population. This probability also increases due to the fact that relatives of patients (especially the first degree of kinship) often have a common habitat with them. Meanwhile, the threshold of susceptibility, this kind of Rubicon, can be crossed not only as a result of the “set” of appropriate genetic information, but also under the influence of certain factors that can provoke the development of a pathological phenotype against the background of such hereditary information that would never have been realized under other conditions. This is how the empirical and often not very thoughtful recommendation of doctors "to change the way of life" receives a theoretical justification. In fact, for close relatives of patients with hereditary diseases, such advice can become, as will be shown below, an important preventive measure. This is of particular importance, since multifactorial diseases or diseases with a hereditary predisposition currently account for 92% of the total human pathology.

Multifactorial diseases, with all their diversity, are characterized by some common features:

high frequency in the population;
the existence of clinical forms that form a continuous series from latent subclinical to pronounced manifestations;
earlier onset and some increase in clinical manifestations in descending generations;
significant gender and age differences in the population frequency of nosological forms;
a relatively low level of concordance for manifest manifestations of the disease in monozygotic twins (60% or less), nevertheless significantly exceeding the corresponding level in dizygotic twins;
inconsistency of inheritance patterns with simple Mendelian models;
the dependence of the degree of risk for the relatives of the patient on the frequency of the disease in the population (it is the higher, the rarer the disease occurs), the risk increases with the birth of each next patient, in addition, it increases as the severity of the disease of the proband increases;
the similarity of clinical and other manifestations of the disease in the next of kin and the proband, which reflects the coefficient of heritability (for polygenic diseases, it exceeds 50-60%).

To date, in addition to the mentioned model of polygenic inheritance with a threshold manifestation, several others have been proposed. All of them are based on determining the degree of accumulation of repeated cases of the disease in the family in comparison with the frequency of the disease in the general population. One of them proceeds only from the additive action of genes. It is based on the assumption that all the genes of the system that determine the development of the disease are subject to minimal mutations that complement each other. At the same time, the manifestation of a pathological trait in a family can vary from zero to maximum, depending on the number of genes that have undergone mutations. Another model suggests that against the background of the additive action of several mutant genes, the disease may arise as a result of the influence of one so-called master gene.

With regard to the most widespread multifactorial diseases in the human population, the clinical genetic method solves the following problems.

A summary assessment of the contribution of heredity to the causes and patterns of development of the disease.
Identification of specific genetic predisposition factors for the development of diseases.
The study of the genetic basis of clinical variability and genetic heterogeneity of diseases (the presence of several forms within any pathology)

The ultimate objectives of such an analysis are the description of the disease under study in exact genetic terms, i.e., the selection of monogenic and multifactorial forms, and the creation of a genetic classification on this basis. Identification of forms of the studied nosological unit, different from the etiological point of view, opens up the possibility of differentiated pathogenetic (and etiological, if a known biochemical defect is known) treatment, as well as individual prognosis, primary and secondary prevention. Therefore, for the differential diagnosis of monogenic diseases and various forms of multifactorial diseases within the same family, in addition to clinical and genealogical analysis, it is also necessary to determine the coefficient of heritability. The latter reflects the contribution (share) of genetic factors to the development of the disease under the combined action of genotypic and environmental factors. Multifactorial diseases are characterized by a heritability coefficient of more than 50%, monogenic - 100%.

In the simplest version, the coefficient of heritability of a disease is the ratio of actually observed pathological features to the theoretically expected frequency of their manifestation in the family, or is the ratio of the observed phenotypic correlation between relatives (c) and the expected, taking into account the proportion of common features in relatives (k). The coefficient is usually expressed as a percentage. As noted above, with an autosomal dominant type of inheritance, the manifestation of the disease in persons of the 1st degree of kinship (parents - children, brothers - sisters) is 0.5 (i.e., 50% of relatives are sick), for persons of the 2nd and 3rd degrees of kinship - respectively 0.25 and 0.125. In this case, the heritability coefficient will be equal to 100%, since we are talking about the exclusively genetic nature of the disease, i.e., the inheritance of one dominant gene or the sum of dominant genes with an additive effect. But since multifactorial diseases are manifested under the influence of not only hereditary, but also adverse environmental factors, the heritability coefficient will always be below 100%, the observed similarity between relatives will be less than theoretically expected. To determine the phenotypic similarity (r), the number of signs of the disease in two or more close relatives (I degree of kinship) is determined, highlighting common similar signs:

N 1.2 r \u003d --------------- n 1 + n 2 - n 1.2
where n 1.2 - the number of signs common to relatives; n 1 - the number of signs in one relative; n 2 - the number of signs in the second, etc. relatives (Rogers-Tanimoto index). In this case, the coefficient of heritability (h) of the disease for relatives of the first degree of kinship: h 2 = r / 0.5 x 100; for relatives of the II degree of kinship: h 2 \u003d r / 0.25 x 100

In recent years, the study of the role of hereditary factors in the genesis of multifactorial pathology has been characterized by a pronounced clinical and genetic direction. The main efforts are aimed at identifying the genetic heterogeneity of multifactorial diseases and traits. For example, duodenal ulcer and gastric ulcer and their age-related variants, distinguished within the traditional classification of the form of peptic ulcer, are multifactorial diseases with a polygenic determination of the hereditary component of predisposition. When studying peptic ulcer with onset in adulthood (after 18 years), it was shown that, compared with gastric ulcer, duodenal ulcer is a genetically more aggravated form. In turn, the child form of duodenal ulcer is genetically even more burdened than the adult form, and among all varieties of the disease it is the form with the greatest contribution of genetic factors (the degree of genetic conditionality is 74%, see Appendix).

A promising direction in the study of the genetics of such diseases is also the discovery of an association between them and genetic markers (monogenically inherited traits), the presence of which could then be used to judge predisposition to this multifactorial disease. Features of diagnosis, clinic, treatment and prevention of multifactorial diseases, in contrast to monogenic and chromosomal diseases, are presented in Table. 3.

Table 3. Main differential diagnostic differences between chromosomal, monogenic and multifactorial diseases
sign	Chromosomal	Monogenic	Multifactorial
genetic nature	Structural and numerical anomalies of gono- and autosomes	Single gene mutation	Polygenic complex
Inheritance mechanism	Mostly newly emerging	Mendelian nature of inheritance	Additive polygenic inheritance
Prevalence	From single descriptions to 1:600	From 1:5,000 to 1:1,000,000 or less	1:1000 to 20:100
Recurrent risk (the risk of having another patient in the family)	In the absence of carriage of a balanced chromosomal anomaly in parents, it is insignificant. In the presence of an anomaly from 2% to 100% (depending on the type of anomaly and the sex of the carrier)	25% to 50% (excluding penetrance)	Varies over a wide range
determined	The presence of balanced chromosomal rearrangements in parents	Type of inheritance	Empirically, depending on the degree of hereditary burden (the number of sick relatives of the I-II degree of kinship, the severity of the disease in relatives, the presence of relatives belonging to the "rarely affected sex", etc.)
depends on:
the number of affected relatives;	Not	Not	Depends
the severity of the clinical picture in sick relatives;	Not	Not	Depends
gender of the proband	Not	With sex-linked inheritance	In some cases, a predominant lesion of one sex is noted, then the risk increases when a relative belonging to the "rarely affected sex" appears in the pedigree
different for children and siblings of the proband	different	different	Identical, since they have an equal share of genes in common with the proband
Diagnostics	Clinical and cytogenetic	Clinical, clinical-genealogical, biochemical	Clinical, clinical and genealogical
Clinic	Multiple congenital malformations	Nonspecific, often systemic, progressive disease	Extreme variability of the picture depending on the degree of hereditary aggravation
Treatment	symptomatic	Etiopathogenetic (with a known biochemical defect); symptomatic (when the defect is unknown)	pathogenic and symptomatic
Treatment efficacy and prognosis	Depends on the specific chromosomal or genomic abnormality	Depends on the severity of a specific biochemical or other defect	Depends on the degree of hereditary burden
Prevention	Prenatal diagnosis (cytogenetic)	Prenatal diagnosis (biochemical) and identification of heterozygous carriers of mutant alleles in the population	Identification of groups of increased genetic risk based on family history and creation of optimal environmental conditions for them with the exclusion of pathogenetic risk factors

Genetics for doctors

General questions of medical genetics Subject and problems Hereditary pathology The role of hereditary and environmental factors in the pathogenesis of diseases General patterns of pathogenesis of hereditary diseases

Patterns of inheritance of human traits and methods for their study Genealogical method Methodology of compilation, pedigree The procedure for collecting genealogical information. Features of the collection of anamnestic data Graphical representation of the pedigree Pedigree analysis Autosomal dominant type of inheritance Autosomal recessive type of inheritance X-linked type of inheritance Multifactorial inheritance Genealogical analysis for multifactorial diseases Risk group for chromosomal pathology Risk group for monogenic diseases Risk group for multifactorial diseases Twin method Population method Chromosomes and chromosomal diseases Down's disease Patau's syndrome (trisomy 13) "Cat's cry" syndrome Sex chromosome anomalies Shereshevsky-Turner syndrome (X0) Triplo-X syndrome (XXX) Klinefelter syndrome (XXY) XYY syndrome

Molecular basis of hereditary pathology Fermentopathy Treatment of hereditary diseases Replacement therapy

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Disrespect for ancestors is the first sign of savagery and immorality.
A.S. Pushkin

Lesson objectives: to introduce students to the genealogical method of studying pedigrees; learn how to write a family tree.

Equipment: tables "Symbols adopted in the construction of the tree of human life", "Pedigree of the royal family".

I. Compilation of pedigrees

Once upon a time, only aristocratic families knew their genealogy. Later, their genealogies were very useful to science - they helped to establish patterns of inheritance of many diseases.

“In our country, for the most part, they don’t know anything about ancestors, they don’t respect family traditions ...” - I. Aksakov wrote this at a time when the Senate had a whole heraldic department that dealt with genealogies of nobles, and the living rooms of each estate were decorated with portraits of ancestors.

Russian philosopher O.P. Florensky considered genealogy to be a kind of pedagogy: "The history of the family should give moral lessons and tasks." He called for active knowledge of his kind, argued that each kind is faced with a historical task “assigned” to it, which it “is called upon to solve”.

The teacher introduces the children to the rules of work on the compilation of pedigrees.

Rule One

The work on the pedigree is endless, it can last a lifetime and will require careful research, so you need to stock up on patience, diligence and accuracy.

1. Very quickly, a huge number of names will open before you, so you need to immediately get a thick notebook with numbered pages and make a table of contents in it.
2. Prepare several folders for papers. You will store letters, photos, notes, documents, etc. in them.
3. Need colored pencils and felt-tip pens.
4. Your archive will gradually grow, so it is advisable to immediately determine the place where you will place it. Anyone who is not too lazy will soon find the first exhibits for the family museum: photographs, personal items.
5. If possible, use a camera, video camera, tape recorder.
6. Get a photo album.

Rule Two

All records, including draft ones, must be kept accurately and in as much detail as possible. The teacher invites the children to draw a family tree and explains how to do it.

Take a pencil, a sheet of paper, draw a square (a generally accepted symbolic image: men - a square, women - a circle). Draw a square at the bottom right - that's you. Mark the box with an arrow and indicate your age (for example, 17 years old). Next, symbolically draw your brother () and sister (). Connect yourself, sister and brother with a common bracket. Now symbolize your parents: father, mother. Connect them with a horizontal line symbolizing marriage (Fig. 1).

Your parents may have brothers and sisters. Let's say your mother has a brother and two sisters, and your father has two brothers. These are your uncles and aunts, add them to the pedigree (Fig. 2).

The next older generation are grandparents on the paternal and maternal lines. They continue your drawing up (fig. 3).

Let's denote the generation of grandparents with number 1, the generation of fathers and mothers with number 2, ourselves and our brothers and sisters with number 3. We symbolically depicted three generations of your family.

Knowing the principle of building a pedigree, you can now continue it horizontally, bringing in the relatives of your future wife and up - vertically - great-grandfathers and great-grandmothers. Well, below the line that connected you and your future wife, you can symbolically designate your future children (Fig. 4).

You have a tree with a highly branched crown. You can, of course, turn the drawing over and turn the crown into a root system. After all, it is not by chance that we use the expression "my roots go back to my family ...", "I come to my roots ...". In a word, it does not matter how you draw a tree.

Rule Three

The branches (roots) of the tree must be absolutely symmetrical, and the number of branches - even. Number of ancestors with each ascending generation doubles: two parents, four grandfathers, eight great-grandfathers, etc. If this series is continued, then the number of ancestors in each ascending generation will be equal to 2 n, where n- a value indicating the number of generations.

The famous American geneticist Kurt Stern believed that all people on earth are related to each other by one degree or another of kinship. This connection becomes especially evident if we consider a number of family trees that have become classic and are widely used in genetics. Moreover, the visibility of these pedigrees is provided by a clear inheritance of some characteristic feature. An example is the pedigree of European royal families descended from Queen Victoria (Fig. 5).

This pedigree demonstrates the transmission of the inherited disease hemophilia (bleeding disorder). Hemophilia affects only males, while women are only carriers of this gene. Queen Victoria “endowed” hemophilia to many men in her family, including Tsarevich Alexei, the son of Nicholas II and Tsarina Alexandra Feodorovna (Alice), who inherited the hemophilia gene from her grandmother, Queen Victoria.

Rule Four

When filling out a family tree, try to ensure that each branch contains a surname, name, patronymic. Remember the state of health of the relatives indicated in it, the characteristics of the character, the fate of each. Ask everyone who knew them about this. Maybe one of them was a long-liver, and someone died early. Write down the dates of birth and death and make notes about past illnesses.

I hope that your parents will be interested in your research and help you.

At the first initial stage of compiling a pedigree, personalities are established - names, surnames, dates of birth and death. Together with the names of the ancestors, we begin to collect material about them: memories of relatives, letters, photographs. And all further work will be reduced not just to the pedigree, but to history of your family.

Task number 1

Draw a chronological scale of major events in our country vertically. Next, build another table in which your ancestors (or some of them) would appear, because you already know what time they lived. From now on, the study of your kind begins, as it were, from two sides.

II. Sources (archives)

All your oral sources are implemented, you have questioned everyone. Where to go next? All data on births, marriages, deaths should be sought in the archives. Here you will need the help of adults.

Task number 2

1. Contact the district archive with a request to provide information about your ancestors. In this case, it is necessary to give the exact name, patronymic and surname of the relative, it is desirable to know the year of birth.
2. Try to visit a local museum in your relative's home country and get some information about him.
3. Write a letter to the regional archive with a request to send the information you are interested in.

Rule Five

When requesting data from archives, museums, and other institutions, provide as much information as possible about your relative and clearly formulate your question.

III. About the trunk

Let's return to the starting point, i.e. to the "foot of the tree", or rather, to you .

Task number 3

1. Start writing a diary. First, get acquainted with the diaries of L. Tolstoy, F. Dostoevsky, M. Prishvin, and other writers and artists. Second, write at least a few lines every day. Read A. Bolotov's notes.
2. Try to write not only about external, but also about internal life, reflect everything that worries you. Don't avoid writing about those around you.
3. Write only the truth, even if it is unpleasant for you.

IV. About the first two branches

It's about your parents: dad and mom. When describing the life of the genus, a mistake is often made. We try to learn as much as possible about those who are no longer alive, and completely forget about those who are nearby. In the meantime, grandpa, grandma, mom and dad can help you.

Rule six

When gathering information, do not divide facts into essential and seemingly insignificant.

Rule Seven

Do not put off for one day what you have planned in the work on the pedigree, especially if it concerns older people.

Rule eight

Until you can determine the significance of this or that document, material, collect everything that concerns your family.

V. About the family archive, museum

Gradually, a family archive begins to form in your home, which can develop into a family museum: photographs, personal belongings of ancestors, dishes, books, clothes, awards, certificates, diplomas, documents, manuscripts. Particularly valuable are items made by the hands of ancestors - household items, sewing, embroidery.

In addition to documents about your family, the surname of your relatives can tell a lot. Learn the origin of your last name.

VI. Features of some families

When studying Russian families, a number of specific features associated with the occupation are distinguished. This specificity largely determines a targeted search for the compilation of a pedigree. This applies to families of priests, military, Cossacks, etc. A special place is occupied by noble families.

A whole section in the history of the genus must be devoted to culture, education, peculiarities of the mind, and character traits.

VII. The historical significance of the genus

We have mentioned far from all the attributes that you can use in the knowledge of your kind. Once again, I note that the knowledge of the genus is infinite, and therefore in each case many issues are resolved individually and it is impossible to predict all decisions on compiling a pedigree.

The reconstructed pedigree will become not only an interesting family heirloom, but also a valuable medical document that you, your children or grandchildren will simply need if you have to go to medical genetic counseling. After all, giving new life is a huge responsibility!

Literature

Kislitsina T.G. Ethics and psychology of family life. - M.: School-Press, 1999.

Barashnev Yu.I. Heredity and health. - M.: Knowledge, 1976.