Chromosomal diseases are ailments of a hereditary nature, which are caused by a change in the structure or number of chromosomes. This group of diseases also includes those that are caused by genomic mutations. There are pathologies due to changes occurring in the sexual cells of the parents.
The concept of chromosomal diseases
This is a large group of congenital ailments, which occupies one of the leading places in the list of hereditary pathologies of man. Cytological studies of materials from early abortions show that human chromosomal diseases can manifest themselves even in embryos. That is, the disease develops in the process of fertilization or in the early stages of fragmentation of the zygote.
Types of chromosomal diseases
Experts are accustomed to divide all the ailments into three large species. Classification of chromosomal diseases depends on the violations:
- ploidy;
- the number of chromosomes;
- structure of chromosomes.
The most common anomalies caused by a violation of ploidy - triploid and tetralopodium. Such changes, as a rule, are fixed only in the material obtained as a result of abortions. Only isolated cases of the birth of children with similar disorders are known, and they always interfered with normal life activity. Triploidy is the result of the fertilization of diploid ovules with haploid spermatozoa or vice versa. Sometimes anomaly is a consequence of the fertilization of one ovum with two spermatozoa.
Chromosome number disorder
In most cases, chromosomal diseases, which resulted in a violation of the number of chromosomes, are manifested by whole monosomy or trisomy. At the last, all three nucleoprotein structures are homologues. At the first anomaly of the number of chromosomes, one of the two available in the set remains normal. The whole monosomy is only on chromosome X, because embryos with other sets die very early - even at the initial stages of intrauterine development.
Disturbance of chromosome structure
The ailments developing against the background of chromosome structure disorder are represented by a large group of syndromes with partial mono- or trisomy. They arise when there are structural changes in the parental sex cells. Such disturbances affect the recombination processes. Because of this, in meiosis, there is a loss or an overabundance of fragments of nucleoprotein structures. Partial chromosomal abnormalities can be observed in any chromosomes.
Causes of chromosomal diseases
Scientists for a long time worked on this issue. As it turned out, the chromosomal mutations of the disease cause. They lead to deviations in the structure and functions of the nucleoprotein structures. Know not only the causes of chromosomal diseases, but also the factors that have the potential to manifest mutations. Value have:
- features of the anomaly involved;
- genotype of the organism;
- type of anomaly;
- the size of the missing or excess genetic material (with structural disturbances);
- the degree of cellular mosaic of the organism (only those cells that have deviations in structure or functions are taken into account).
Chromosomal Diseases - List
Each year, it is updated with new names - the ailments are investigated constantly. Considering what are chromosomal diseases, the most famous today is:
- Down Syndrome. It develops due to trisomy. That is, because in cells there are three copies of the 21st chromosome, instead of two. As a rule, the "superfluous" structure is transferred to the newborn from the mother.
- Klinefelter's syndrome. This chromosomal disease does not appear immediately at birth, but only after puberty. As a result of this deviation, men receive from one to three X chromosomes and lose the opportunity to have children.
- Myopia. Myopia is a genetic deviation, because of which the image is formed not where it is supposed to be - on the retina of the eye - but in front of it. The main reason for this problem is an increase in the eyeball in length.
- Color blindness. Color blinds can not distinguish one or several colors at once. The reason - in the "defective" chromosome X, received from the mother. In the stronger sex, this deviation occurs more often, because as for men, the X-structure is only one, and "to correct the defect" - as it happens in the case of female organisms - their cells can not.
- Hemophilia. Chromosomal diseases can be manifested by a violation of blood coagulability.
- Migraine. The disease, manifested by severe pain in the head, is also inherited.
- Cystic fibrosis. For this ailment is a violation of the glands of external secretion. People with this diagnosis suffer from excessive sweating, abundant separation of mucus, accumulating in the body and interfering with the correct operation of the lungs.
Methods for diagnosis of chromosomal diseases
Genetic consultations, as a rule, seek help from such methods:
- Genealogical. It is the collection and analysis of data on the patient's pedigree. This method makes it possible to understand whether the disease is hereditary and, if so, determine the type of inheritance.
- Antenatal diagnosis. Identifies hereditary disorders of the fetus, which is in the womb at the time of 14-16 weeks of pregnancy. If abnormalities in the amniotic fluid are detected by autosomes, abortion can be made.
- Cytogenetic. Used to identify syndromes and abnormalities.
- Biochemical. Clarifies the disease and helps identify mutated genes.
Treatment of chromosomal diseases
Therapy does not always help to get rid of the disease, but it can slow it down. Chromosomal abnormalities of the fetus are treated by such methods:
- Dietotherapy. Assumes the addition or exclusion from the diet of certain substances.
- Drug therapy. It is used to influence the mechanisms of enzyme synthesis.
- Surgery. Helps cope with congenital heart defects , various bone defects and deformities.
- Substitution therapy. Its essence is in the compensation of those substances that are not synthesized in the body independently.
Frequency of chromosomal diseases
Very often, human chromosomal abnormalities occur in materials obtained as a result of spontaneous abortions made in the first trimester. The overall frequency of violations in the population is actually not so great and is about 1%. Children with genetic abnormalities can also be born in healthy parents. Newborn girls and boys, as medical practice shows, are affected by chromosomal diseases with the same frequency.