The human body is a complex multifaceted system that operates at various levels. In order for organs and cells to work in the correct mode, certain substances must participate in specific biochemical processes. This requires a solid foundation, that is, the correct transfer of the genetic code. It is the inherent hereditary material that controls the development of the embryo.
However, changes in hereditary information sometimes occur that appear in large associations or relate to individual genes. Such errors are called gene mutations. In some cases, this problem relates to the structural units of the cell, that is, to whole chromosomes. Accordingly, in this case, the error is called chromosome mutation.
Each human cell normally contains the same number of chromosomes. They are united by the same genes. The complete set is 23 pairs of chromosomes, but in germ cells they are 2 times smaller. This is due to the fact that during fertilization, the fusion of the sperm and the egg should be a complete combination of all the necessary genes. Their distribution does not occur randomly, but in a strictly defined order, and such a linear sequence is absolutely the same for all people.
Chromosomal mutations contribute to a change in their number and structure. Thus, an extra chromosome may appear or, conversely, they will be missed. This imbalance can cause abortion or contribute to the occurrence of chromosomal diseases.
Types of chromosomes and their abnormalities
A chromosome is a carrier of hereditary information in a cell. It is a doubled DNA molecule in complex with histones. The formation of chromosomes occurs in prophase (at the time of cell division). However, during the metaphase period, they are more convenient to study. Chromosomes, which consist of two chromatids, that is, are connected by a primary constriction, are located at the equator of the cell. The primary constriction divides the chromosome into 2 sections of the same or different lengths.
The following types of chromosomes are distinguished:
- metacentric - with shoulders of equal length;
- submetacentric - with shoulders of unequal length;
- acrocentric (rod-shaped) - with one short and the other with long shoulders.
Anomalies are relatively large and small. Research methods vary depending on this parameter. Some cannot be detected with a microscope. In such cases, the differential staining method is used, but only when the affected area is estimated in millions of nucleotides. Only by establishing the nucleotide sequence can small mutations be detected. And larger violations lead to a pronounced effect on the human body.
In the absence of one of the chromosomes, the anomaly is called monosomy. The extra chromosome in the body is trisomy.
Chromosomal diseases
Chromosomal diseases are genetic pathologies that occur as a result of chromosome abnormalities. They arise due to changes in the number of chromosomes or large rearrangements
When medicine was still far from the modern level of development, it was believed that a person has 48 chromosomes. And only in 1956 they were able to correctly calculate, number and identify the relationship between the violation of the number of chromosomes and some hereditary diseases.
After 3 years, the French scientist J. Lejeune discovered that impaired mental development in people and resistance to infections are directly related to the genomic mutation. It was about the extra 21 chromosome. She is one of the smallest, but a large number of genes are concentrated in it. Extra chromosome was observed in 1 out of 1000 newborns. This chromosomal disease is by far the most studied and is called Down Syndrome.
In the same 1959, it was studied and proved that the presence of an extra X chromosome in men leads to Kleinfelter's disease, in which a person suffers from mental retardation and infertility.
However, despite the fact that chromosomal abnormalities have been observed and studied for a long time, even modern medicine is not able to treat genetic diseases. But methods for diagnosing such mutations have been quite modernized.
Causes of Extra Chromosome
An anomaly is the only reason for the appearance of 47 chromosomes instead of the 46 ones. Medical experts have proved that the main reason for the appearance of an extra chromosome is the age of the future mother. The older the pregnant woman, the greater the likelihood of chromosome nondisjunction. For this reason alone, women are advised to give birth before age 35. In the event of pregnancy after the onset of this age should undergo examination.
Factors that contribute to the appearance of an extra chromosome include the level of anomalies, which has increased in the whole world, the degree of environmental pollution, and much more.
It is believed that an extra chromosome occurs if there were similar cases in the genus. This is just a myth: studies have shown that parents whose children suffer from chromosomal disease have a completely healthy karyotype.
Diagnosis of the appearance of a child with a chromosomal abnormality
Recognition of chromosome abnormalities, the so-called screening of aneuploidy, reveals a lack or excess of chromosomes in the embryo. Pregnant women over 35 are advised to undergo a procedure for obtaining amniotic fluid samples. If a violation of the karyotype is found, then the expectant mother will need to terminate the pregnancy, since the born child will suffer a serious illness all her life in the absence of effective treatment methods.
The violation of chromosomes is mainly of maternal origin, so you should analyze not only the cells of the embryo, but also the substances that form during maturation. This procedure is called the diagnosis of genetic disorders in the polar bodies.
Down Syndrome
The scientist who first described Mongolism is Down. The extra chromosome, the gene disease in the presence of which is necessarily developing, has been widely studied. With Mongolism, trisomy occurs on the 21 chromosome. That is, in a sick person, instead of the set 46, 47 chromosomes are obtained. The main symptom is a lag in development.
Children who have an extra chromosome experience serious difficulties in mastering the material in the school, so they need an alternative teaching methodology. In addition to mental, there is a deviation in physical development, namely: slanting eyes, flat face, wide lips, flat tongue, shortened or extended limbs and feet, a large accumulation of skin in the neck. Life expectancy reaches an average of 50 years.
Patau Syndrome
Trisomy also includes Patau syndrome, in which 3 copies of 13 chromosomes are observed. A distinctive feature is a violation of the central nervous system or its underdevelopment. Patients have multiple malformations, including congenital heart disease. More than 90% of people with Patau syndrome die in their first year of life.
Edwards Syndrome
This anomaly, like the previous ones, refers to trisomy. In this case, we are talking about the 18th chromosome. Edwards syndrome is characterized by various disorders. Basically, patients have bone deformity, an altered shape of the skull, problems with the respiratory system and the cardiovascular system. Life expectancy is usually about 3 months, but some babies live up to a year.
Endocrine diseases with chromosome abnormalities
In addition to the above syndromes of chromosomal abnormality, there are others in which a numerical and structural anomaly is also observed. Such diseases include the following:
- Triploidy is a rather rare disorder of chromosomes, in which their modal number is 69. Pregnancy usually ends with an early miscarriage, but when the child survives, it lasts no more than 5 months, numerous birth defects are observed.
- Wolf-Hirschhorn syndrome is also one of the rarest chromosomal abnormalities that develops due to a deletion of the distal end of the short arm of the chromosome. The critical area of this disorder is 16.3 on chromosome 4p. Characteristic features are developmental problems, stunted growths, cramps and typical facial features
- Prader-Willi syndrome - the disease is very rare. With such an abnormality of the chromosomes, 7 genes or some parts of them on the 15th paternal chromosome do not function or are completely removed. Signs: scoliosis, strabismus, delayed physical and intellectual development, fatigue.
How to raise a child with a chromosomal disease?
Raising a child with congenital chromosomal diseases is not easy. In order to make your life easier, you must adhere to some rules. First, despair and fear must be overcome immediately. Secondly, there is no need to waste time searching for the guilty one, he simply does not exist. Thirdly, it is important to decide what kind of help the child and family need, and then turn to specialists for medical, psychological and pedagogical help.
In the first year of life, diagnosis is extremely important, since during this period motor function develops. With the help of professionals, the child will quickly acquire motor abilities. It is necessary to objectively examine the baby for pathology of vision and hearing. Also, the child should be monitored by a pediatrician, neuropsychiatrist and endocrinologist.
Parents are advised to join a special Association in order to receive valuable practical advice from people who have overcome this situation and are ready to share.
The carrier of an extra chromosome is usually friendly, which facilitates his upbringing, and he also tries to earn the approval of an adult as much as he can. The level of development of a special baby will depend on how hard they will teach him basic skills. Sick children, although lagging behind the rest, but require a lot of attention. It is always necessary to encourage the independence of the child. It is necessary to instill self-service skills by example, and then the result will not be long in coming.
Children with chromosomal diseases are endowed with special talents that need to be revealed. It can be music lessons or drawing. It is important to develop the baby’s speech, play active and motor-developing games, read, and also accustom to the mode and accuracy. If you show your child all his tenderness, care, attention and affection, he will answer the same.
Can it be cured?
To date, it is impossible to cure chromosomal diseases; Each proposed method is experimental, and their clinical effectiveness has not been proven. To achieve success in the development, socialization and acquisition of skills helps systematic medical and educational assistance.
A sick child should be monitored by specialists all the time, since medicine has reached the level at which it is able to provide the necessary equipment and various types of therapy. Teachers will apply modern approaches in the education and rehabilitation of the baby.