The human body is a complex multifaceted system that functions 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 transmission of the genetic code. It is the laid hereditary material that controls the development of the embryo.
However, sometimes there are changes in hereditary information that appear in large associations or concern individual genes. Such errors are called gene mutations. In some cases, this problem refers to the structural units of the cell, that is, to whole chromosomes. Accordingly, in this case, the error is called a chromosome mutation.
Every human cell normally contains the same number of chromosomes. They share the same genes. The complete set is 23 pairs of chromosomes, but in germ cells they are 2 times less. This is due to the fact that during fertilization, the fusion of the spermatozoonand the egg must represent 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 a miscarriage or contribute to chromosomal disorders.
Types of chromosomes and their anomalies
Chromosome is the carrier of hereditary information in the cell. It is a double DNA molecule in complex with histones. The formation of chromosomes occurs in prophase (by the time of cell division). However, during the metaphase period, it is more convenient to study them. Chromosomes, which consist of two chromatids, that is, 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 arms of equal length;
- submetacentric - with arms of unequal length;
- acrocentric (rod-shaped) - with one short and the other long arms.
Anomalies are relatively large and small. Research methods vary depending on this parameter. Some are impossible to detect with a microscope. In such cases, the differential staining method is used, but only when the affected area is measured in millions of nucleotides. Only thanksthe establishment of the nucleotide sequence can reveal small mutations. And larger violations lead to a pronounced effect on the human body.
If one of the chromosomes is missing, the anomaly is called monosomy. An extra chromosome in the body is trisomy.
Chromosomal diseases
Chromosomal diseases are genetic pathologies that occur as a result of abnormal chromosomes. They occur 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 count, 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 found that mental disorders in people and resistance to infections are directly related to genomic mutation. It was an extra 21 chromosome. She is one of the smallest, but a large number of genes are concentrated in her. An extra chromosome was observed in 1 in 1000 newborns. This chromosomal disease is by far the most studied and is called Down syndrome.
In the same 1959, it was studied and proven that the presence of an extra X chromosome in men leads to Klinefelter'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 does notable to treat genetic diseases. But the methods for diagnosing such mutations are quite modernized.
Causes of an extra chromosome
Anomaly is the only reason for the appearance of 47 chromosomes instead of the prescribed 46. Medical experts have proven that the main reason for the occurrence of an extra chromosome is the age of the expectant mother. The older the pregnant woman, the greater the likelihood of nondisjunction of chromosomes. For this reason alone, women are advised to give birth before the age of 35. If you become pregnant after this age, you should be tested.
The factors that contribute to the appearance of an extra chromosome include the level of anomaly, which has increased in the whole world, the degree of environmental pollution and much more.
There is an opinion that an extra chromosome occurs if there were similar cases in the family. This is just a myth: studies have shown that parents whose children suffer from a chromosomal disease have a perfectly he althy karyotype.
Diagnosis of the appearance of a child with a chromosomal abnormality
Recognition of abnormal number of chromosomes, the so-called screening for aneuploidy, reveals the lack or excess of chromosomes in the embryo. Pregnant women over 35 years of age are advised to undergo a procedure for obtaining a sample of amniotic fluid. If a violation of the karyotype is detected, then the expectant mother will need to terminate the pregnancy, since the born child will suffer from a serious illness all her life in the absence of effective methods of treatment.
Chromosomal disorders are mainly of maternal origin, so it is necessary to analyze not only the cells of the embryo, but also the substances that are formed during maturation. This procedure is called the diagnosis of genetic disorders by polar bodies.
Down Syndrome
The scientist who first described Mongolism is Down. An extra chromosome, the disease of genes in the presence of which necessarily develops, has been widely studied. With Mongolism, trisomy occurs on chromosome 21. That is, in a sick person, instead of the prescribed 46, 47 chromosomes are obtained. The main symptom is developmental delay.
Children who have an extra chromosome experience serious learning difficulties in school, so they need an alternative teaching method. In addition to mental, there is also a deviation in physical development, namely: slanting eyes, a flat face, wide lips, a flat tongue, shortened or widened 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 chromosome 13 are observed. A distinctive feature is a violation of the activity 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 the first year of life.
Edwards Syndrome
This anomaly, like the previous ones,related to trisomy. In this case, we are talking about chromosome 18. 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 around 3 months, but some babies live up to a year.
Endocrine diseases with chromosome anomalies
In addition to the listed syndromes of chromosomal abnormality, there are others in which there is also a numerical and structural anomaly. These diseases include the following:
- Triploidy is a rather rare disorder of chromosomes, in which their modal number is 69. Pregnancy usually ends in an early miscarriage, but if the child survives for no more than 5 months, numerous birth defects are observed.
- Wolf-Hirschhorn syndrome is also one of the rarest chromosomal anomalies, which develops due to a deletion of the distal end of the short arm of the chromosome. The critical region for this disorder is 16.3 on chromosome 4p. Characteristics are developmental problems, stunting, seizures and typical facial features
- Prader-Willi Syndrome - the disease is very rare. With such an abnormality of chromosomes, 7 genes or some of their parts 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 disorder?
Raising a child with congenital chromosomal diseases is not easy. In order to make your life easier, you need to follow some rules. First, you should immediately overcome despair and fear. Secondly, there is no need to waste time looking for the culprit, 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 and psychological and pedagogical help.
During the first year of life, diagnosis is extremely important, as motor function develops during this period. With the help of professionals, the child will quickly acquire motor skills. It is necessary to objectively examine the baby for pathology of vision and hearing. Also, the child should be observed by a pediatrician, psychoneurologist and endocrinologist.
Parents are encouraged to join a special Association in order to receive valuable practical advice from people who have overcome a similar situation and are ready to share.
The carrier of the extra chromosome is usually friendly, which makes it easier to raise him, and he also tries to earn the approval of an adult to the best of his ability. The level of development of a special baby will depend on how hard they teach him basic skills. Sick children, although lagging behind the rest, require a lot of attention. It is always necessary to encourage the independence of the child. Self-care skills should be taught by example, and then the result will not be long in coming.
Children with chromosomal disorders are endowed with special talents,which needs to be revealed. It could be music or painting. It is important to develop the baby's speech, play active games that develop motor skills, read, and also accustom to the regime and accuracy. If you show all your tenderness, care, attentiveness and affection to the child, 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. Systematic medical and pedagogical assistance helps to achieve success in development, socialization and acquisition of skills.
A sick child should be observed by specialists all the time, as 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 teaching and rehabilitation of the baby.
