As you know, all the appearance and other features of the baby depend on the set of genes that he received from both parents. For most of us, the issue of heredity is interesting only for determining the color of the eyes and hair of the future baby, but the importance of genetics does not end there. IN Lately Even at the stage of planning a child, future parents are strongly recommended to seek help from a geneticist who will determine the likelihood of birth healthy baby exactly this couple. Such a specialist will help you calculate possible risk development of various genetic diseases transmitted by inheritance.
What is genetic inheritance?
The nucleus of each cell in our body contains twenty-three pairs of chromosomes, which contain all hereditary information. We receive half of them from the mother’s body along with the egg, and half from the father’s body along with the sperm. The fusion of these germ cells leads to the birth of a new life. If some gene of the parents is pathogenic, it can be passed on to the baby. If the carrier of such a code is only the father or only the mother, then the likelihood of transmission is significantly reduced.
In general, the chance of a child developing a genetic disease is only three to five percent. However, parents need not to rely on chance, but to take planning for the baby very seriously.
Let's try to figure out what hereditary human genetic diseases exist that are inherited.
Down's disease
The most common genetic disease Down's disease is generally considered to be the case, as statistics show that it affects one in seven hundred newborns. This diagnosis is usually made by a neonatologist in the maternity hospital during the first five to seven days of life. To confirm this status of the baby, a study of the baby’s karyotype (set of chromosomes) is carried out. With Down syndrome, a child has one more chromosome - forty-seven. This disease develops equally often in boys and girls.
Shershevsky-Turner disease
This disease develops only in girls. Its first signs become noticeable only at the age of ten to twelve and are expressed in short stature and low-set hair on the back of the head. Doctors are usually consulted due to lack of menstruation. Over time, the disease leads to some problems in mental development. With Shershevsky-Turner disease, a girl is missing one X chromosome in her karyotype.
Klinefelter's disease
This disease is diagnosed exclusively in males. Most often it is found in the age range from sixteen to eighteen years. Patients are tall - more than one hundred and ninety centimeters, often have some mental retardation and especially long arms, disproportionate to the body, which cover chest. A karyotype study shows one more X chromosome, in some cases it may also be detected by the presence of other extra chromosomes - Y, XX, XY, etc. The main symptom of Klinefelter's disease is infertility.
Phenylcuthonuria
This disease is considered to be one of the most common genetic diseases. With this pathology, the body is not able to absorb the amino acid phenylalanine, which leads to its accumulation in the body. Toxic concentrations of this substance negatively affect brain activity, different organs and systems. The patient has a significant delay in mental and physical development, seizures, dyspeptic-type problems, as well as dermatitis. To correct phenylketonuria, a special diet is used; babies are given special amino acid mixtures that do not contain phenylalanine.
Cystic fibrosis
This disease is also considered relatively common. It is manifested by damage to all organs that produce mucus - the bronchopulmonary system, digestive tract, liver, sweat, salivary and gonads suffer. Patients exhibit symptoms chronic inflammation lungs, as well as bronchi, which are combined with dyspeptic problems - diarrhea, which is followed by constipation, nausea, etc. Therapy involves taking enzyme preparations, as well as anti-inflammatory medications.
Hemophilia
This disease is diagnosed exclusively in boys, although women are carriers of the affected gene. Hemophilia is characterized by problems with blood clotting, which is fraught with a variety of complications and disorders. With this diagnosis, even a small cut is accompanied by prolonged bleeding, and a bruise leads to the formation of a huge subcutaneous hematoma. Injuries of this nature can be fatal. Hemophilia is treated by administering to the patient the clotting factor he or she lacks. Therapy should continue throughout life.
We looked at only a few of the most well-known and common genetic diseases that are inherited. In fact, their list is much longer. Therefore, all couples who are planning to have children, even before pregnancy, need to consult with a qualified geneticist who can foresee possible risks for their common child.
Not only can they be inherited external signs, but also diseases. Malfunctions in the genes of ancestors ultimately lead to consequences in the offspring. We will talk about the seven most common genetic diseases.
Hereditary properties are passed on to descendants from ancestors in the form of genes arranged in blocks called chromosomes. All cells of the body, with the exception of sex cells, have a double set of chromosomes, half of which comes from the mother, and the second part from the father. Diseases caused by certain malfunctions in genes are hereditary.
Myopia
Or myopia. A genetically determined disease, the essence of which is that the image is formed not on the retina, but in front of it. The most common cause of this phenomenon is considered to be increased length eyeball. As a rule, myopia develops in adolescence. At the same time, a person sees perfectly near, but poorly sees into the distance.
If both parents are nearsighted, then the risk of developing myopia in their children is over 50%. If both parents have normal vision, then the probability of developing myopia is no more than 10%.
Studying myopia, employees of the Australian National University in Canberra came to the conclusion that myopia is inherent in 30% of Caucasians and affects up to 80% of Asians, including residents of China, Japan, South Korea etc. Having collected data from more than 45 thousand people, scientists identified 24 genes associated with myopia, and also confirmed their connection with two previously established genes. All these genes are responsible for the development of the eye, its structure, and the transmission of signals in the eye tissue.
Down syndrome
The syndrome, named after the English physician John Down, who first described it in 1866, is one of the forms chromosomal mutation. Down syndrome affects all races.
The disease is a consequence of the fact that in cells there are not two, but three copies of the 21st chromosome. Geneticists call this trisomy. In most cases, the extra chromosome is passed on to the child from the mother. It is generally accepted that the risk of having a child with Down syndrome depends on the age of the mother. However, because young births in general are more common, 80% of all children with Down syndrome are born to women under the age of 30.
Unlike genetic disorders, chromosomal disorders are random failures. And there can be only one person in a family suffering from such a disease. But here, too, there are exceptions: in 3-5% of cases, rarer translocation forms of Down syndrome are observed, when the child has a more complex structure of the chromosome set. A similar variant of the disease can be repeated in several generations of the same family.
According to information charitable foundation Downside Up, about 2,500 children with Down syndrome are born in Russia every year.
Klinefelter syndrome
Another chromosomal disorder. For about every 500 newborn boys, there is one with this pathology. Klinefelter syndrome usually appears after puberty. Men suffering from this syndrome are infertile. In addition, they are characterized by gynecomastia - an increase in mammary gland with hypertrophy of glands and adipose tissue.
The syndrome got its name in honor of the American doctor Harry Klinefelter, who first described the clinical picture of the pathology in 1942. Together with endocrinologist Fuller Albright, he found out that if normally women have a pair of sex chromosomes XX, and men have XY, then with this syndrome in men there are from one to three additional X chromosomes.
Colorblindness
Or color blindness. It is hereditary, much less often acquired. Expressed in the inability to distinguish one or more colors.
Color blindness is associated with the X chromosome and is transmitted from a mother, the owner of a “broken” gene, to her son. Accordingly, up to 8% of men and no more than 0.4% of women suffer from color blindness. The fact is that in men, the “marriage” in the only X chromosome is not compensated for, since, unlike women, they do not have a second X chromosome.
Hemophilia
Another disease that sons inherit from their mothers. The story of the descendants of the English Queen Victoria from the Windsor dynasty is widely known. Neither she herself nor her parents suffered from this serious illness associated with blood clotting disorders. Presumably, the gene mutation occurred spontaneously, due to the fact that Victoria’s father was already 52 years old at the time of her conception.
Victoria's children inherited the fatal gene. Her son Leopold died of hemophilia at age 30, and two of her five daughters, Alice and Beatrice, were carriers of the ill-fated gene. One of Victoria's most famous hemophiliac descendants is her granddaughter's son, Tsarevich Alexei, the only son of the last Russian Emperor, Nicholas II.
Cystic fibrosis
A hereditary disease that manifests itself in disruption of the exocrine glands. It is characterized by increased sweating, secretion of mucus, which accumulates in the body and interferes with the child’s development, and, most importantly, prevents the lungs from functioning properly. Likely death due to respiratory failure.
According to the Russian branch of the American chemical and pharmaceutical corporation Abbott, average duration the lifespan of patients with cystic fibrosis is European countries 40 years, in Canada and the USA - 48 years, in Russia - 30 years. A well-known example is the French singer Gregory Lemarchal, who died at the age of 23. Presumably, Frederic Chopin also suffered from cystic fibrosis, and died as a result of lung failure at the age of 39.
A disease mentioned in ancient Egyptian papyri. Characteristic symptom Migraines are episodic or regular severe attacks of headache in one side of the head. Roman doctor Greek origin Galen, who lived in the 2nd century, called the disease hemicrania, which translates as “half a head.” The word “migraine” comes from this term. In the 90s In the 20th century, it was found that migraine is predominantly caused by genetic factors. A number of genes have been discovered that are responsible for the inheritance of migraine.
Every healthy person has 6-8 damaged genes, but they do not disrupt cell functions and do not lead to disease, since they are recessive (non-manifest). If a person inherits two similar abnormal genes from his mother and father, he becomes ill. The probability of such a coincidence is extremely low, but it increases sharply if the parents are relatives (that is, they have a similar genotype). For this reason, the incidence of genetic abnormalities is high in closed populations.
Every gene in human body responsible for the production of a specific protein. Due to the manifestation of a damaged gene, the synthesis of an abnormal protein begins, which leads to impaired cell function and developmental defects.
A doctor can determine the risk of a possible genetic anomaly by asking you about diseases of relatives “up to the third generation” on both your side and your husband’s side.
There are a great many genetic diseases, some of which are very rare.
List of rare hereditary diseases
Here are the characteristics of some genetic diseases.
Down syndrome (or trisomy 21)- a chromosomal disease characterized by mental retardation and impaired physical development. The disease occurs due to the presence of the third chromosome in the 21st pair (in total, a person has 23 pairs of chromosomes). It is the most common genetic disorder, affecting approximately one in 700 births. The incidence of Down syndrome increases in children born by women over 35 years old. Patients with this disease have a special appearance and suffer from mental and physical retardation.
Turner syndrome- a disease that affects girls, characterized by the partial or complete absence of one or two X chromosomes. The disease occurs in one in 3,000 girls. Girls with this condition are usually very short and their ovaries do not function.
X trisomy syndrome- a disease in which a girl is born with three X chromosomes. This disease occurs on average in one in 1000 girls. Trisomy X syndrome is characterized by slight mental retardation and, in some cases, infertility.
Klinefelter syndrome- a disease in which a boy has one extra chromosome. The disease occurs in one boy out of 700. Patients with Klinefelter syndrome, as a rule, are tall and do not have any noticeable external developmental abnormalities (after puberty, facial hair growth is difficult and the mammary glands are slightly enlarged). The intelligence of patients is usually normal, but speech impairments are common. Men suffering from Klinefelter syndrome are usually infertile.
Cystic fibrosis- a genetic disease in which the functions of many glands are disrupted. Cystic fibrosis affects only Caucasian people. Approximately every twentieth a white man has one damaged gene, which, if manifested, can cause cystic fibrosis. The disease occurs if a person receives two such genes (from the father and from the mother). In Russia, cystic fibrosis, according to various sources, occurs in one newborn out of 3500-5400, in the USA - in one out of 2500. With this disease, the gene responsible for the production of a protein that regulates the movement of sodium and chlorine through cell membranes is damaged. Dehydration occurs and the viscosity of the gland secretion increases. As a result, a thick secretion blocks their activity. In patients with cystic fibrosis, protein and fat are poorly absorbed, and as a result, growth and weight gain are greatly reduced. Modern treatment methods (taking enzymes, vitamins and a special diet) allow half of patients with cystic fibrosis to live more than 28 years.
Hemophilia- a genetic disease characterized by increased bleeding due to a deficiency of one of the blood clotting factors. The disease is inherited by female line, while affecting the vast majority of boys (on average, one in 8,500). Hemophilia occurs when the genes responsible for the activity of blood clotting factors are damaged. With hemophilia, frequent hemorrhages in the joints and muscles are observed, which can ultimately lead to their significant deformation (that is, to a person’s disability). People with hemophilia should avoid situations that could lead to bleeding. People with hemophilia should not take medications that reduce blood clotting (for example, aspirin, heparin, and some pain relievers). To prevent or stop bleeding, the patient is given a plasma concentrate containing a large amount of the missing coagulation factor.
Tay Sachs disease- a genetic disease characterized by the accumulation of phytanic acid (a product of fat breakdown) in tissues. The disease occurs mainly among Ashkenazi Jews and French Canadians (one in 3,600 newborns). Children with Tay-Sachs disease early age are delayed in development, then paralysis and blindness occur. As a rule, patients live up to 3-4 years. Treatment methods of this disease does not exist.
From parents, a child can acquire not only a certain eye color, height or face shape, but also inherited ones. What are they? How can you detect them? What classification exists?
Mechanisms of heredity
Before talking about diseases, it is worth understanding what they are. All information about us is contained in the DNA molecule, which consists of an unimaginably long chain of amino acids. The alternation of these amino acids is unique.
The fragments of a chain of DNA are called genes. Each gene contains integral information about one or more characteristics of the body, which is transmitted from parents to children, for example, skin color, hair, character trait, etc. When they are damaged or their work is disrupted, genetic diseases that are inherited occur.
DNA is organized into 46 chromosomes or 23 pairs, one of which is the sex chromosome. Chromosomes are responsible for gene activity, copying, and recovery from damage. As a result of fertilization, each couple has one chromosome from the father and another from the mother.
In this case, one of the genes will be dominant, and the other will be recessive or suppressed. To put it simply, if the father’s gene responsible for eye color turns out to be dominant, then the child will inherit this trait from him, and not from the mother.
Genetic diseases
Inherited diseases occur when disturbances or mutations occur in the mechanism for storing and transmitting genetic information. An organism whose gene is damaged will pass it on to its descendants in the same way as healthy material.
In the case when the pathological gene is recessive, it may not appear in the next generations, but they will be its carriers. The chance that it will not manifest itself exists when a healthy gene also turns out to be dominant.
Currently, more than 6 thousand hereditary diseases are known. Many of them appear after 35 years, and some may never make themselves known to the owner. Diabetes mellitus, obesity, psoriasis, Alzheimer's disease, schizophrenia and other disorders occur with extremely high frequency.
Classification
Genetic diseases that are inherited have great amount varieties. To divide them into separate groups, the location of the violation, causes, clinical picture, nature of heredity.
Diseases can be classified according to the type of inheritance and location of the defective gene. So, it is important whether the gene is located on the sex or non-sex chromosome (autosome), and whether it is suppressive or not. Diseases are distinguished:
- Autosomal dominant - brachydactyly, arachnodactyly, ectopia lentis.
- Autosomal recessive - albinism, muscular dystonia, dystrophy.
- Limited by gender (observed only in women or men) - hemophilia A and B, color blindness, paralysis, phosphate diabetes.
The quantitative and qualitative classification of hereditary diseases distinguishes genetic, chromosomal and mitochondrial types. The latter refers to DNA disorders in mitochondria outside the nucleus. The first two occur in DNA, which is found in the cell nucleus, and have several subtypes:
Monogenic | Mutations or absence of a gene in nuclear DNA. | Marfan syndrome, adrenogenital syndrome in newborns, neurofibromatosis, hemophilia A, Duchenne myopathy. |
Polygenic | Predisposition and action | Psoriasis, schizophrenia, ischemic disease, cirrhosis, bronchial asthma, diabetes. |
Chromosomal |
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Changes in chromosome structure. | Miller-Dicker, Williams, Langer-Gidion syndromes. |
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Change in the number of chromosomes. | Down's, Patau's, Edwards', Klifenter's syndromes. |
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Causes
Our genes tend not only to accumulate information, but also to change it, acquiring new qualities. This is a mutation. It occurs quite rarely, approximately 1 time in a million cases, and is transmitted to descendants if it occurs in germ cells. For individual genes, the mutation frequency is 1:108.
Mutations are natural process and form the basis of the evolutionary variability of all living beings. They can be useful and harmful. Some help us better adapt to the environment and way of life (for example, the opposite thumb hands), others lead to diseases.
The occurrence of pathologies in genes is increased by physical, chemical and biological. Some alkaloids, nitrates, nitrites, have this property. nutritional supplements, pesticides, solvents and petroleum products.
Among physical factors there are ionizing and radioactive radiation, ultraviolet rays, excessively high and low temperatures. As biological reasons rubella viruses, measles, antigens, etc. appear.
Genetic predisposition
Parents influence us not only through upbringing. It is known that some people are more likely to develop certain diseases than others due to heredity. Genetic predisposition to diseases occurs when one of the relatives has abnormalities in genes.
The risk of a particular disease in a child depends on his gender, because some diseases are transmitted only through one line. It also depends on the person's race and the degree of relationship with the patient.
If a person with the mutation gives birth to a child, the chance of inheriting the disease will be 50%. The gene may well not manifest itself in any way, being recessive, and in the case of marriage with a healthy person, its chances of being passed on to descendants will be already 25%. However, if the spouse also has such a recessive gene, the chances of its manifestation in the descendants will again increase to 50%.
How to identify the disease?
The genetic center will help to detect the disease or predisposition to it in time. Usually everyone has one major cities. Before taking the tests, a consultation is held with a doctor to find out what health problems are observed in relatives.
A medical genetic examination is carried out by taking blood for analysis. The sample is carefully examined in the laboratory for any abnormalities. Expectant parents usually attend such consultations after pregnancy. However, it is worth coming to the genetic center during its planning.
Hereditary diseases seriously affect the mental and physical health child, affect life expectancy. Most of them are difficult to treat, and their manifestation can only be corrected medical supplies. Therefore, it is better to prepare for this even before conceiving a baby.
Down syndrome
One of the most common genetic diseases is Down syndrome. It occurs in 13 cases out of 10,000. This is an anomaly in which a person has not 46, but 47 chromosomes. The syndrome can be diagnosed immediately at birth.
The main symptoms include a flattened face, raised corners of the eyes, short neck and lack muscle tone. Ears, as a rule, small, the eye shape is oblique, the shape of the skull is irregular.
Sick children experience concomitant disorders and diseases - pneumonia, ARVI, etc. Exacerbations may occur, for example, loss of hearing, vision, hypothyroidism, heart disease. With downism it is slowed down and often remains at the level of seven years.
Constant work, special exercises and medications significantly improve the situation. There are many cases where people with a similar syndrome were quite able to lead an independent life, find work and achieve professional success.
Hemophilia
A rare hereditary disease that affects men. Occurs once in 10,000 cases. Hemophilia has no cure and occurs as a result of a change in one gene on the sex X chromosome. Women are only carriers of the disease.
The main characteristic is the absence of a protein that is responsible for blood clotting. In this case, even a minor injury causes bleeding that is not easy to stop. Sometimes it manifests itself only the next day after the injury.
Queen Victoria of England was a carrier of hemophilia. She passed the disease on to many of her descendants, including Tsarevich Alexei, the son of Tsar Nicholas II. Thanks to her, the disease began to be called “royal” or “Victorian”.
Angelman syndrome
The disease is often called “happy doll syndrome” or “Parsley syndrome”, as patients experience frequent outbursts of laughter and smiling, and chaotic hand movements. This anomaly is characterized by disturbances in sleep and mental development.
The syndrome occurs once in 10,000 cases due to the absence of certain genes on the long arm of chromosome 15. Angelman disease develops only if genes are missing from the chromosome inherited from the mother. When the same genes are missing from the paternal chromosome, Prader-Willi syndrome occurs.
The disease cannot be completely cured, but it is possible to alleviate the symptoms. For this purpose, physical procedures and massages are performed. Patients do not become completely independent, but during treatment they can take care of themselves.
This problem is long-standing and very serious, although no more than five percent of newborn children suffer from hereditary diseases.
Hereditary diseases are the result of a defect in the genetic apparatus of cells passed from parents to children and are already present during intrauterine development fetus Diseases such as cancer, diabetes, heart defects and many other diseases can be hereditary. Congenital diseases may arise as a result abnormal development genes or chromosomes. Sometimes it only takes a few abnormal cells to appear for a person to subsequently develop a malignant disease.
Hereditary and congenital diseases in children
Concerning medical term“genetic diseases” then it applies to those cases. When the moment of damage to the cells of the body occurs already at the stage of fertilization. Such diseases arise, among other things, due to a violation of the number and structure of chromosomes. This destructive phenomenon occurs as a result of improper maturation of the egg and sperm. These diseases are sometimes called chromosomal. These include such serious illnesses as Down syndrome, Klinefelter syndrome, Edwards syndrome and others. Modern medicine almost 4 thousand are known various diseases arising on the basis of genetic abnormalities. Another interesting fact is that 5 percent of people have at least one defective gene in their bodies, but are completely healthy people.
Terminology in the article
A gene is the initial unit of heredity, which is part of a DNA molecule that influences the formation of protein in the body, and therefore the signs of the state of the body. Genes are presented in binary form, that is, one half is transmitted from the mother, and the other from the father.
Deoxyribonucleic acid (DNA) is a substance found in every cell. It carries all the information about the state and development of a living organism, be it a person, an animal or even an insect.
Genotype is a set of genes acquired from parents.
Phenotype - set characteristic features state of the body during its development.
Mutations are persistent and irreversible changes in the genetic information of an organism.
Quite common are monogenic diseases, in which only one gene responsible for a certain function of the body is damaged. Due to the fact that there are many such diseases, a certain classification has been adopted in medicine, which looks like this.
Autosomal dominant diseases.
This group includes diseases that occur when there is only one copy of a defective gene. That is, only one of the patient’s parents is sick. Thus, it becomes clear that the offspring of such a sick person have a 50% chance of inheriting the disease. This group of diseases includes diseases such as Marfan syndrome, Huntington's disease and others.
Autosomal recessive diseases.
This group includes diseases that occur due to the presence of two defective copies of a gene. In this case, those who gave birth to a sick child can be absolutely healthy, but at the same time be carriers of one copy of a defective, mutated gene. In such a situation, the risk of having a sick child is 25%. This group of diseases includes diseases such as cystic fibrosis, sickle cell anemia and other ailments. Such carriers usually appear in closed societies, as well as in the case of related marriages.
X-linked dominant diseases.
This group includes diseases that occur due to the presence of defective genes on the female sex X chromosome. Boys are more likely to suffer from such diseases than girls. Although a boy born from a sick father may not pass the disease on to his offspring. As for the girls, they all have mandatory the defective gene will be present. If the mother is sick, then the probability of inheriting her disease is the same for boys and girls and is 50%.
X-linked recessive diseases.
This group includes those diseases that are caused by mutations of genes located on the X chromosome. IN in this case Boys are at greater risk of inheriting the disease than girls. Also, a sick boy may not subsequently pass the disease on to his children. Girls will also have one copy of the defective gene in any case. If a mother is a carrier of a defective gene, then she has a 50% chance of giving birth to a sick son or a daughter who will become a carrier of such a gene. This group of diseases includes diseases such as hemophilia A, Duchenne muscular dystrophy and others.
Multifactorial or polygenic genetic diseases.
This includes those diseases that arise as a result of a malfunction of several genes at once, and under the influence external conditions. The heredity of these diseases is manifested only relatively, although the diseases often have familial characteristics. These are diabetes, heart disease and some others.
Chromosomal diseases.
This includes those diseases that arise due to a violation of the number and structure of chromosomes. If such signs are present, women often experience miscarriages and undeveloped pregnancies. Children of such women are born with both mental and physical abnormalities. Such cases, alas, occur quite often, namely in one out of twelve fertilizations. The results of such sad statistics are not visible due to termination of pregnancy at a certain stage of fetal development. As for born children, statistics say that one out of one hundred and fifty newborns is born with this disease. Already in the first trimester of pregnancy, half of women with chromosomal diseases of the fetus experience miscarriages. This indicates that the treatment is ineffective.
Before talking about the prevention of hereditary and congenital diseases, it is worth spending a little time on issues related to polygenic or multifactorial diseases. These diseases occur in adults and often cause concern about the feasibility of having offspring and the likelihood of diseases passing on from parents to children. The most common diseases in this group are such diseases.
Diabetes mellitus types 1 and 2 .
This disease has partially hereditary characteristics. Type 1 diabetes can also develop due to viral infection or due to prolonged nervous disorders. Examples have been noted where diabetes-1 arose as a result of an allergic reaction to aggressive external environment and even on medical supplies. Some people with diabetes are carriers of a gene that is responsible for the likelihood of developing the disease in childhood or adolescence. As for type 2 diabetes, the hereditary nature of its occurrence is clearly visible. The highest probability of developing type 2 diabetes is already in the first generation of the carrier’s descendants. That is, his own children. This probability is 25%. However, if the husband and wife are also relatives, then their children will necessarily inherit parental diabetes. The same fate awaits identical twins, even if their diabetic parents are not related.
Arterial hypertension.
This disease is the most typical of the category of complex polygenic diseases. In 30% of cases of its occurrence, there is a genetic component. As arterial hypertension develops, at least fifty genes take part in the disease and their number grows over time. The abnormal effect of genes on the body occurs under the influence of environmental conditions and the body’s behavioral reactions to them. In other words, despite the body’s hereditary predisposition to the disease arterial hypertension, healthy image life in treatment plays a huge role.
Violation of fat metabolism.
This disease is the result of the influence of genetic factors together with a person’s lifestyle. Many genes are responsible for metabolism in the body, for the formation of fat mass and for the strength of a person’s appetite. Failure of just one of them can lead to the appearance of various diseases. Externally, a disorder of fat metabolism manifests itself in the form of obesity in the patient’s body. Among obese people, fat metabolism is impaired in only 5% of them. This phenomenon can be observed en masse in some ethnic groups, which confirms the genetic origin of this disease.
Malignant neoplasms.
Cancerous tumors do not appear as a result of heredity, but haphazardly and one might even say by chance. Nevertheless, isolated cases have been recorded in medicine when cancerous tumors arose precisely as a result of heredity. These are mainly cancers of the breast, ovaries, colon and blood. The reason for this is a congenital mutation of the VYACA1 gene.
Mental development disorder.
The most common cause of mental retardation is hereditary factor. Parents of a mentally retarded child are often carriers of a number of mutant genes. Often, the interaction of individual genes is disrupted or disturbances in the number and structure of chromosomes are observed. Characteristic symptoms include Down syndrome, fragile X syndrome and phenylketonuria.
Autism.
This disease is associated with impaired brain functionality. It is characterized by poorly developed analytical thinking, stereotypical behavior of the patient and his inability to adapt to society. The disease is detected by the age of three years of a child’s life. Doctors associate the development of this disease with improper synthesis of proteins in the brain due to the presence of gene mutations in the body.
Prevention of congenital and hereditary diseases
It is customary to separate preventive measures against such diseases into two categories. These are primary and secondary measures.
The first category includes such measures as identifying the risk of disease at the stage of planning conception. It also includes measures for diagnosing fetal development using systematic examinations of a pregnant woman.
When planning a pregnancy, in order to prevent hereditary diseases, it is worth contacting the regional clinic, where the “Family and Marriage” database stores archival data on the health of the spouses’ ancestors. As for medical genetic consultation, it is necessary if the spouses have chromosomal changes, hereditary diseases, and, of course, if abnormal development of the fetus or an already born child is detected. In addition, such consultation must be obtained if the husband and wife are related. Consultation is extremely necessary for those couples who have previously experienced miscarriages or children who were stillborn. It will also be useful for all women who will give birth for the first time at the age of 35 or more.
At this stage, a study is made of the pedigree of both spouses, based on the medical data available in the archive on the health of previous generations of the husband and wife. In this case, it is possible to identify with almost absolute accuracy whether there is a likelihood of a hereditary disease occurring in the unborn child, or whether there is none. Before going for a consultation, spouses must ask their parents and relatives in as much detail as possible about the diseases that occurred in previous generations of the family. If the family history contains hereditary diseases, then you should definitely tell your doctor about this. This will make it easier for him to determine the necessary preventive measures.
Sometimes at the stage primary prevention it is necessary to analyze the state of the chromosome set. This analysis is performed on both parents, since the child will inherit half of the chromosome from mom and dad. Unfortunately completely healthy people may be carriers of balanced chromosomal rearrangements and not even suspect the presence of such a deviation in their bodies. If a child inherits a chromosomal rearrangement from one of the parents, then the likelihood of serious illnesses will be quite high.
Practice shows that in such a family the risk of having a child with a balanced chromosomal rearrangement is about 30%. If the spouses have rearrangements in the chromosome set, then during pregnancy with the help of PD it is possible to prevent the birth of an unhealthy child.
As part of the primary prevention of congenital anomalies nervous system child, a widely used method is the administration of folic acid, which is a solution of vitamins in water. Before pregnancy, a sufficient amount of folic acid enters the woman’s body during good nutrition. If she adheres to any diet, then, of course, the supply of acid may not be in the amount required by the body. In pregnant women, the body's need for folic acid increases by one and a half times. It is not possible to ensure such an increase through diet alone.
By the way, this is the only vitamin that during pregnancy should enter the body in greater quantities than before pregnancy. It is possible to satisfy the pregnant woman’s body’s need for folic acid only through its additional use. Folic acid has unique properties. So, additional intake of this vitamin two months before conception and during the first two months of pregnancy reduces the likelihood of abnormal abnormalities in the child’s central nervous system by three times! Usually the doctor prescribes four standard tablets per day. If the first child had some kind of deviation in the development of the central nervous system, and the woman decided to give birth again, then in this case she needs to increase the amount of folic acid taken by two, or even two and a half times.
Secondary prevention of congenital and hereditary diseases
This includes preventive measures that are applied already in the case when it is known for sure that the fetus in the body of a pregnant woman is developing with pathological abnormalities from the norm. If such a sad circumstance is discovered, the doctor must inform both parents about this and recommend certain procedures to correct the development of the fetus. The doctor must explain exactly how the child will be born and what awaits him as he grows up. After this, the parents decide for themselves whether it is worth giving birth to a child or whether it would be better and more humane to terminate the pregnancy in time.
Two methods are used to diagnose the condition of the fetus. These are non-invasive measures that do not require physical intervention and invasive measures in which a sample of fetal tissue is taken. The essence of non-invasive measures is to test the mother's blood and ultrasound diagnostics her body and that of the fetus. Recently, doctors have mastered the technology of taking blood tests from the fetus. The sample is taken from the mother's placenta, into which fetal blood penetrates. This process is quite complicated, but also quite effective.
Maternal blood testing is usually done at the end of the first - beginning of the second trimester of pregnancy. If two or three substances are present in the blood in abnormal quantities, then this may be a sign of the presence of a hereditary disease. In addition, at the end of the first trimester of pregnancy, human chorionic gonadotropin is determined in the mother. This is a pregnancy hormone, which in a woman’s body is produced by the placenta and in turn produces serum protein A. In the second trimester of pregnancy, an analysis is done for the content of hCG, alpha-fetoprotein, and unbound (free) estriol.
A set of such measures in world medicine is called a “triple panel”, and the overall technique is called “biochemical screening”.
During the first trimester of pregnancy, the concentration of hCG in the blood serum doubles daily. After the complete formation of the placenta, this indicator stabilizes and remains unchanged until childbirth. HCG supports the production in the ovaries of hormones necessary for the normal course of pregnancy. In the mother’s blood, not the entire hormone molecule is determined, but only the p-subunit. If the fetus has chromosomal diseases, in particular Down syndrome, the content of the hormone in the mother’s blood serum is significantly increased.
Whey protein A is produced in the mother's body in the tissue of the placenta. If the fetus has a chromosomal disease, then the amount of protein will be underestimated. It should be noted that such changes can only be recorded from the tenth to fourteenth week of pregnancy. Subsequently, the level of protein in the mother’s blood serum returns to normal.
Alpha fetoprotein (AFP) is produced already in the tissues of the embryo and continues in the tissues of the fetus. The function of this component is not fully understood. It is determined in a woman’s blood serum or amniotic fluid as a marker birth defects central nervous system, kidneys or anterior abdominal wall. It is known that when oncological diseases this protein is found in the blood serum of both adults and children. As the fetus develops, this protein passes from the fetal kidneys into the mother's blood through the placenta. The nature of the change in its amount in the mother’s serum depends both on the presence of a chromosomal disease in the fetus and on some features of the course of the pregnancy itself. Thus, the analysis of AFP without assessing the functionality of the placenta is not of decisive importance from the point of view of diagnostic accuracy. Nevertheless, AFP as a biochemical marker of congenital diseases has been well studied.
AFP is most accurately determined during the second trimester of pregnancy, namely between the sixteenth and eighteenth weeks. Until this time, from the point of view of diagnostic accuracy, it makes no sense to determine this protein. If the fetus has birth defect central nervous system or anterior abdominal wall, then the level of AFP in the mother’s blood serum will be significantly higher than normal. If the fetus suffers from Down or Edwards syndrome, then, on the contrary, this indicator will be lower than normal.
The hormone estriol is produced by both the maternal placenta and the fetus itself. This hormone ensures the normal course of pregnancy. The level of this hormone in the mother's blood serum during normal conditions also increases progressively. If the fetus has a chromosomal disease, then the level of unbound estriol in the mother’s body is significantly lower than the norm during normal pregnancy. Studying the level of the hormone estriol allows one to determine with sufficient accuracy the likelihood of having a child with a hereditary disease. However, only experienced specialists can interpret the results of the analysis, because this process is quite complex.
Carrying out biochemical screening is a very important procedure. In addition, this method has a number of advantages. It does not require surgical intervention in the mother’s body and is not a technologically complex process. At the same time, effectiveness this study very high. However, this method is not without its drawbacks. In particular, it allows you to determine only the degree of probability of the occurrence of a congenital disease, and not the fact of its presence. In order to accurately identify this presence, additional diagnostic testing is required. The saddest thing is that the results of biochemical screening can be absolutely normal, but the fetus has a chromosomal disorder. This technique requires the most accurate determination of the date of fertilization and is not suitable for studying multiple pregnancies.
Ultrasonography
Devices for ultrasound diagnostics are constantly being improved. Modern models allow you to view the fetus even in a three-dimensional image format. These devices have been used in medicine for quite a long time and during this time it has been fully proven that they do not have any effect. negative impact neither on the health of the fetus nor on the health of the mother. According to medical standards in force in Russian Federation, ultrasound examination of pregnant women is carried out three times. The first time this is done during the period 10 - 14 weeks of pregnancy, the second 20 - 24 and the third 32 - 34 weeks. The first study determines the duration of pregnancy, the nature of its course, the number of fetuses and describes in detail the condition of the mother’s placenta.
Using an ultrasound, the doctor determines the thickness of the collar space along the back surface of the fetal neck. If the thickness of this part of the fetal body is increased by three or more millimeters, then in this case there is a possibility that the child will develop chromosomal diseases, including Down syndrome. In this case, the woman is prescribed additional examination. At this stage of pregnancy, the doctor checks the degree of development of the fetus's nasal bone. If the fetus has a chromosomal disease, the nasal bone will be underdeveloped. With this detection, additional examination of the mother and fetus is also required.
During the second study, at 10-24 weeks of pregnancy, the fetus is examined in detail for the presence of developmental defects and signs of chromosomal diseases. The condition of the placenta, cervix and amniotic fluid is also assessed.
Almost half of fetal malformations can be detected during ultrasound examination during the period 20 - 24 weeks of pregnancy. Moreover, the remaining half may in fact not be detected at all by any of the currently known diagnostics. Thus, it is impossible to say that diagnostics can one hundred percent determine the presence of a congenital disease in a fetus. Nevertheless, it is necessary to do it, at least for the sake of that half of the cases that are determined with accuracy.
It is understandable that parents are impatient to find out who will be born to them, a girl or a boy. It should be said that conducting research just for the sake of curiosity is not recommended, especially since in five percent of cases it is not possible to accurately determine the sex of the child.
Very often, the doctor prescribes repeated examinations for pregnant women, and this scares many. However, there is no need to panic because only 15% of repeat examinations are associated with the presence of signs of abnormal fetal development. Of course, in this case, the doctor must tell both parents about this. In other cases, repeated examination is associated either with a safety net or with the peculiarity of the location of the fetus.
At the stage of pregnancy at 32-34 weeks, the research process determines the rate of fetal development and identifies signs of defects that are characteristic of late manifestation. If any pathology is detected, the pregnant woman is asked to have a tissue sample of the fetus or placenta analyzed.
Chorionic villus (placenta) biopsy can be done between 8 and 12 weeks of pregnancy. This procedure is performed on an outpatient basis. No more than five to ten milligrams of tissue is taken for analysis. Such an insignificant amount is quite enough to analyze the number and structure of chromosomes. This method makes it possible to accurately determine the presence or absence of a chromosomal disease.
Amniocentesis is a technique for taking amniotic fluid for analysis. They begin to be produced in the body of a pregnant woman soon after conception. The amniotic fluid contains fetal cells. During analysis, these cells can be isolated and examined. Typically, this test is performed between 16 and 20 weeks of pregnancy. In this case, no more than 20 milliliters of water is taken, which is absolutely safe for the woman and the fetus. Another method of “early amniocentesis” is also used, which can be performed at the end of the first trimester of pregnancy. Lately it has been rarely used. This is due to the fact that in last years Cases of fetal limb defects have become more frequent.
Cordocentesis is another name for intrauterine umbilical cord puncture. This technique is used to obtain a fetal blood sample for further laboratory research. This test is usually performed between 20 and 24 weeks of pregnancy. The amount of blood required for a full analysis is about three to five grams.
It should be said that all of the above methods are, to a certain extent, fraught with unpleasant consequences. In particular, statistics show that after such studies, one to two percent of women have a termination of pregnancy. Thus, these tests are best performed when the likelihood of congenital diseases in the fetus is too high. At the same time, the importance of these tests cannot be denied, since they make it possible to identify even one altered gene in the fetal body. And yet, invasive methods are gradually becoming a thing of the past, and they are being replaced by new technologies. They allow fetal cells to be isolated from the mother's blood.
Thanks to the development of a method such as in vitro fertilization in the treatment of infertility, it has become possible to carry out preimplantation diagnostics. Its essence is as follows. The egg is artificially fertilized in a laboratory and placed in an incubator for a certain time. Here cell division occurs, that is, the formation of an embryo essentially begins. It is at this time that you can take one cell for research and conduct full analysis DNA. In this way, it is possible to find out exactly how the fetus will subsequently develop, including from the perspective of the likelihood of hereditary diseases.
At the end of the article, it should be emphasized that the main goal of all these studies is not only to identify the presence or absence of a hereditary disease in the fetus, but also to promptly warn parents and sometimes relatives of the unborn baby about this. It often happens that there is no hope for correction of any pathology identified in the fetus’s body, just as there is no hope that the born child will be able to develop normally. In such a tragic situation, doctors recommend parents to artificially terminate the pregnancy, although final decision Parents decide on this matter. However, they need to take into account that the tragedy of termination of pregnancy is not commensurate with the tragedy that will happen at the birth of a defective child.
