How many chromosomes does Down have, what does it affect, how does it affect a person's life?

47 instead of 46 chromosomes - this is the main difference between a person born with Down syndrome from other people. Excessive genetic material at down leads to the formation of many characteristics of such people. This applies to appearance, the state of internal organs, mental development and the ability to adapt in human society.

With such a pathology, the world is born one child for 700-800 births. And this happens even in the families of very healthy people.

More than a hundred years ago

The first thing the doctors paid attention to was the unusual appearance of some children who were lagging behind in development from their peers and had similar health problems.

Altered skull shape, short neck, face on which the nose, eyebrows, chin are implicitly expressed; short nose; slanting eyes with upturned corners; disproportionately short arms and legs, small palms - all of these signs occur to varying degrees.

The doctor who noticed the pattern in the late 19th century was named John Down, and he lived in Great Britain. At first, because of the "eastern" shape of the eyes, the pathology was called "Mongoloid syndrome".

But, when about a hundred years after the observations of the British doctor the reason was discovered the appearance of such anomalies, it became clear that pathology has nothing to do with a person's belonging to a particular race.

The "culprit", as scientists have found out, is an extra chromosome. If an ordinary, healthy, according to medicine, person, 23 pairs of chromosomes (in total - 46 pieces), then the person suffering from Down syndrome has one unpaired chromosome, which increases total up to 47. This conclusion was reached when studies showed how many chromosomes do children with a certain set of features.

Such an excess becomes the cause of the development of many disorders in the body: external and internal. Excess genetic material disrupts the formation processes of organs and systems, as well as the brain, which leads to abnormalities.

Symptoms of the syndrome

In addition to external manifestations, a number of internal disorders in the body develop. About 40 percent of these people are born with a heart defect.

They have reduced muscle tone, which is noticeable by the constantly open mouth. After age eight, two-thirds develop cataracts. They are much more at risk of developing leukemia or Alzheimer's disease.

Disruptions in the work of the digestive system are not uncommon. Weak immunity. Hearing, thyroid gland and so on may suffer.

There is evidence that malignant tumors in such people develop less frequently than in others, but there is no full-fledged research on this topic.

Mental capacity

Babies who are born with Down syndrome have a different brain function than those with 46 chromosomes.

• Mental development is noticeably slower, and as you grow, this difference with peers increases. In most cases, the level of mental development is fixed at the stage of seven years in comparison with what is considered normal.
• It is difficult for a person to pronounce sounds, which is explained by low muscle tone. Speech is slurred and vocabulary is limited
• It is difficult for such people to think abstractly, to fantasize, to imagine images. They understand and analyze what they can see.
• It is difficult to concentrate on one thing for a long time.

What is the reason?

A genetic malfunction, leading to the appearance of excess genetic material in the human genetic code, can occur in different variants and at different stages of the formation and development of the fetus.

• As observations show, in most cases, the 21st chromosome is tripled. This means that each cell of the fetus, and then the entire human body, contains three 21 chromosomes together two, like most people. This happens even in the body of future parents, when their sex cells are formed.

According to researchers, 90 percent of such cases occur in the mother's oocytes, 10 percent are "responsible" for the father's sperm. Statistics show that if in the mother before the age of 24, the likelihood of developing the syndrome is 1x5000, then after 45 years - 1x19.

If a germ cell with an excessive number of chromosomes takes part in fertilization, then the fetus inherits 47 instead of 46. This variant of the genetic malfunction is called trisomy 21. And he occurs in 95-99 percent cases of detecting children with Down syndrome.

• A few more percent falls on later genetic mutations, which do not occur at the beginning of the embryo formation process, but later. In this situation, some of the cells will have 46 chromosomes, and the other - 47. It depends on the ratio what manifestations will be, that is, violations will affect only some individual parts of the body. This leads to the fact that it is much more difficult to detect abnormalities before the birth of a baby than with trisomy 21, since external signs may be completely absent. This variety is called mosaic.
• About 2-3 percent of cases are caused by the so-called Robertsonian translocation. In this case, 21 chromosomes are attached to another, usually to the 14th in the karyotype of either a woman or a man.

Risk factors

Why genetics fails, medicine cannot say for sure. There is a version that one of the provoking factors is radiation exposure organism of one of the parents. Other possible sources of negative impact on human genetic material are also considered. So far, no serious research has been carried out on these topics. In assessing the risk of developing pathology, physicians are guided mainly by statistics.

The numbers show several patterns.

1. Children with Down syndrome are more likely to be born to womenwho are older. After 25 years, the number of cases increases fivefold. After thirty - more than twenty.
2. Men are more at risk of conceiving a fetus with this pathology when they turn 42: sperm quality decreases with age.
3. Marriages between relatives also increase the likelihood that genetic defects will develop.
4. In some forms, there is a risk of inherited disorders, but this is very low.
5. Bad habits in the form of smoking tobacco, taking drugs and alcohol, say doctors, directly affect the state of the germ cells. The birth of children with genetic abnormalities in people with such habits is noted more often than in those who do not.

Life forecast

In the overwhelming majority of cases, it is possible to diagnose Down syndrome in the fetus during ultrasound examination. According to statistics, of all pathologies confirmed by ultrasound, about 30 percent are likely to lead to miscarriage: about a third of such pregnancies end in miscarriage.

A hundred years ago, most people who were born with this anomaly died in the first few years of life - due to numerous violations of the internal organs. significant portion lived 20-25 years, few lived longer.

With the development of medicine, it became possible to diagnose the presence of pathology in the womb, prepare for the birth of such a child and create all the necessary conditions to preserve and improve the condition his health. People with Down syndrome who are cared for and loved now live to be sixty or more.

Parents decision

The decision whether a baby with Down syndrome will be born, if such a diagnosis is made by ultrasound examination of the fetus, is made by the parents. It happens that the subjective assessment of the doctor conducting the ultrasound is incorrect, and the baby is born absolutely healthy.

There is a more reliable way to find out how things are - to do non-invasive prenatal DNA test. It can be performed starting from the ninth week of pregnancy, and the accuracy of the study is called high. The possibilities of modern medicine in countries with developed economies have led to the fact that the frequency of birth of babies in whom this pathology is detected has decreased up to one per 1100 births.

Statistics show that about 92 percent women who find out that their future child has been diagnosed with this disorder, decide to terminate the pregnancy. The main reason is the fear of negative attitudes towards such children on the part of society. Of those who have such children, 94 percent leave them in maternity hospitals.

Only six percent of babies get a chance for parental attention. As a rule, in such families, the baby is looked after and tried to develop his abilities to the maximum.

Syndrome treatment

Official medicine has not yet learned how to treat genetic disorders. Research is being conducted, the task of which is to learn how to "turn off", make inactive extra chromosome. Such work, which was performed on stem cells, gave a positive result. But this is only the first stage: there is still a lot to be done before clinical trials before being introduced into everyday medical practice.

While people suffering from the syndrome receive treatment that is aimed at reducing the manifestations of physiological and mental disorders. Complex work with such patients in some cases gives excellent results in the form of significant increasing the level of mental development, improving health status and fairly acceptable adaptation to society.