Genetic diseases inherited. Medico-genetic examination

From the parents the child can acquire not onlya certain color of the eyes, the growth or shape of the face, but also genetic diseases transmitted by inheritance. What are they like? How can you find them? What classification of hereditary diseases exists?

Mechanisms of heredity

Before talking about the diseases, it is worthto 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.

hereditary genetic diseases

In this case, one of the genes will be dominant, andanother recessive or repressed. It's simpler if the father, the gene responsible for eye color, is dominant, then the child will inherit this attribute from it, not from the mother.

Genetic diseases

Diseases transmitted by inheritance arise,when in the mechanism of storage and transfer 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.

genetic center

In the case where the pathological gene isrecessive, 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 thousandhereditary diseases. Many of them manifest themselves after 35 years, and some may never tell themselves to the master. With an extremely high frequency of diabetes, obesity, psoriasis, Alzheimer's disease, schizophrenia and other disorders.


Genetic diseases transmitted byinheritance, 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 by typeinheritance and location of a 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 - brachidactyly, arachnodactyly, ectopia of the lens.
  • Autosomal recessive - albinism, muscular dystonia, dystrophy.
  • Limited sex (observed only in women or men) - haemophilia A and B, color blindness, paralysis, phosphate-diabetes.

Quantitative and qualitative classificationGenetic, chromosome and mitochondrial species are isolated from hereditary diseases. The latter refers to the violation of DNA in the mitochondria outside the nucleus. The first two occur in DNA, which is located in the nucleus of the cell, and have several subspecies:






Mutations or the absence of a gene in nuclear DNA.

Marfan syndrome, adrenogenital syndrome in newborns, neurofibromatosis, hemophilia A, Duchenne myopathy.


Predisposition and effect of exogenous factors.

Psoriasis, schizophrenia, ischemic disease, cirrhosis, bronchial asthma, diabetes mellitus.


Changing the structure of chromosomes.

Syndromes of Miller-Dicker, Williams, Langer-Gidion.

Changing the number of chromosomes.

Syndromes of Down, Patau, Edwards, Klaifenter.


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

Mutations are a natural process andconstitute 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.

genetic predisposition

The occurrence of pathologies in genes increasesphysical, 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 ionizingand 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 education. It is known that some people are more likely to have some diseases than others because of heredity. Genetic predisposition to diseases 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 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 has a child, thenthe 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 to be transferred to the offspring will be already 25%. 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 orpredisposition 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 bytaking 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.

 classification of hereditary diseases

Hereditary diseases seriously affect themental and physical health of the child, affect life expectancy. Most of them are difficult 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 geneticdiseases - 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 auricles are usually small, the incision is oblique, the irregular shape of the skull.

 what is genetic heredity

In ill children, accompanyingdisorders 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 anddrugs greatly 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.


A rare hereditary disease that affectsmen. 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.

adrenogenital syndrome in newborns

The main characteristic is the absenceprotein, 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.

The English Queen Victoria was the bearerhemophilia. She transferred the disease to many of her descendants, including the Tsarevich Alexei - the son of Tsar Nicholas II. Thanks to her illness, they began to be called "royal" or "Victorian".

Angelmann's Syndrome

The disease is often called the "happy syndrome"dolls "or" Parsley Syndrome ", as patients often experience outbursts of laughter and smiles, chaotic movements of hands. This abnormality is characterized by a disturbance of sleep and mental development.

medical genetic examination

The syndrome occurs once in 10 000 cases due toabsence 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, butease the manifestation of symptoms possible. For this, physical procedures and massages are carried out. Completely independent patients do not become, but during treatment they can serve themselves.

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