Genetic diseases inherited. Medico-genetic examination

From parents, a child can acquire not only a certain eye color, height or shape of a person, but also genetic diseases that are inherited. What are they like? How can you find them? What classification of hereditary diseases exists?

Mechanisms of heredity

Before talking about diseases, it is worthwhile to understand what is genetic inheritance. 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.

Fragments of the DNA chain are called genes. In each gene there is an integral information about one or more signs of the organism, which is transmitted from parents to children, for example, skin color, hair, character trait, etc. If they are damaged or their work is disrupted, genetic diseases are inherited.

DNA is organized in 46 chromosomes or 23 pairs, one of which is sexual. Chromosomes are responsible for the activity of genes, their copying, as well as recovery from damage. As a result of fertilization, each pair contains one chromosome from the father, and the other from the mother.

In this case, one of the genes will be dominant, and the other is recessive or suppressed. It is simpler if the father, the gene responsible for eye color, is dominant, then the child will inherit this feature from it, not from the mother.

Genetic diseases

Passed by inheritance of the disease arise when in the mechanism of storage and transmission of genetic information there are violations or mutations. An organism whose gene is damaged will transmit it to its offspring in the same way as healthy material.

In the case where the pathological gene is recessive, it may not manifest itself in the next generations, but they will be its carriers. The chance that a dominant gene does not manifest itself exists when a healthy gene is also dominant.

Currently, more than 6 thousand hereditary diseases are known. Many of them manifest themselves after 35 years, and some may never tell themselves to the master. With an extremely high incidence of diabetes, obesity, psoriasis, Alzheimer's disease, schizophrenia and other disorders.

Classification

Genetic diseases, inherited, have a huge number of varieties. To separate them into separate groups, the location of the disorder, the causes, the clinical picture, the nature of the heredity can be taken into account.

Diseases can be classified according to the type of inheritance and location of the defective gene. So, it is important, the gene is located in the genital or non-sexual chromosome (autosome), and whether it is overwhelming or not. Allocate diseases:

• Autosomal dominant - brachodactyly, arachnodactyly, ectopia of the lens.
• Autosomal recessive - albinism, muscular dystonia, dystrophy.
• Limited sex (observed only in women or men) - hemophilia A and B, color blindness, paralysis, phosphate-diabetes.

The quantitative-qualitative classification of hereditary diseases distinguishes gene, chromosome and mitochondrial species. The latter refers to the violation of DNA in the mitochondria outside the nucleus. The first two occur in DNA, which is in the nucleus of the cell, and have several subspecies:

Causes

Our genes are inclined not only to accumulate information, but also to change it, acquiring new qualities. This is a mutation. It occurs quite rarely, approximately 1 time per million cases, and is transmitted to offspring, if occurred in the sex cells. For individual genes, the mutation frequency is 1: 108.

Mutations are a natural process and constitute the basis of the evolutionary variability of all living beings. They can be useful and harmful. Some help us to better adapt to the environment and the way of life (for example, the opposed thumb of the hand), others lead to diseases.

The occurrence of pathologies in the genes is increased by physical, chemical and biological mutagenic factors. This property is possessed by some alkaloids, nitrates, nitrites, some food additives, pesticides, solvents and petroleum products.

Among the physical factors are ionizing and radioactive radiation, ultraviolet rays, excessively high and low temperatures. As biological causes are the viruses of rubella, measles, antigens, etc.

Genetic predisposition

Parents influence us not only by upbringing. It is known that some people are more likely to have some diseases than others because of heredity. Genetic predisposition to disease occurs when one of the relatives has a disorder in the genes.

The risk of a specific disease in a child depends on its sex, because some diseases are transmitted only along one line. It also depends on the race of a person and on the degree of kinship with a sick person.

If a person with a mutation is born a child, then the chance of inheriting the disease will be 50%. The gene may well not show itself at all, being recessive, and in the case of marriage with a healthy person, its chances of being transferred to the offspring will be 25% already. However, if the spouse also owns such a recessive gene, the chances of its manifestation in offspring will again increase to 50%.

How to identify the disease?

In time to detect the disease or predisposition to it will help the genetic center. Usually such is in all major cities. Before passing the tests, a consultation with a doctor is conducted to find out what health problems are observed with relatives.

Medico-genetic examination is carried out by taking blood for analysis. The sample is carefully studied in the laboratory for any deviations. Future parents usually attend such consultations after the onset of pregnancy. However, it is worthwhile to come to the genetic center during its planning.

Hereditary diseases seriously affect the mental and physical health of the child, affect life expectancy. Most of them are hard to treat, and their manifestation is only adjusted by medical means. Therefore, it is better to prepare for this before the conception of the baby.

Down Syndrome

One of the most common genetic diseases is Down's syndrome. It occurs in 13 cases out of 10,000. This is an anomaly in which a person does not have 46, but 47 chromosomes. Diagnosis of the syndrome can be done immediately at birth.

Among the main symptoms are a flattened face, raised corners of the eyes, short neck and lack of muscle tone. The ears are usually small, the incision is oblique, the irregular shape of the skull.

Patients with children have comorbid disorders and diseases - pneumonia, acute respiratory infections, etc. There may be exacerbations, for example, hearing loss, vision, hypothyroidism, heart disease. With daunism, mental development is slowed and often remains at the level of seven years.

Permanent work, special exercises and drugs significantly improve the situation. There are many cases where people with a similar syndrome could easily lead an independent life, find work and achieve professional success.

Hemophilia

A rare hereditary disease that affects men. It occurs once for 10 000 cases. Hemophilia is not treated and occurs as a result of a change in one gene in the sex X chromosome. Women are only carriers of the disease.

The main characteristic is the absence of protein, which is responsible for blood clotting. In this case, even a minor injury causes bleeding, which is not easy to stop. Sometimes it manifests itself only the day after the injury.

English Queen Victoria was a carrier of hemophilia. She transferred the disease to many of her descendants, including the Tsarevich Alexei - the son of Tsar Nicholas II. Thanks to her, the disease was called "royal" or "Victorian".

Angelmann's Syndrome

The disease is often called "happy doll syndrome" or "Parsley syndrome", as patients often experience outbreaks of laughter and smiles, chaotic hand movements. With this anomaly is characterized by a violation of sleep and mental development.

The syndrome occurs once in 10 000 cases due to the absence of some genes in the long arm of the 15th chromosome. Angellman's disease develops only if the genes are absent in the chromosome, which is derived from the mother. When the same genes are absent in the paternal chromosome, Prader-Willi syndrome arises.

The disease can not be cured completely, but it is possible to alleviate the symptoms. For this, physical procedures and massages are carried out. Completely independent patients do not become, but during treatment they can serve themselves.