How many chromosomes does a person have?
Since the beginning of the twentieth century, researchers have been looking for the answer to the question of how many chromosomes a person has. For a start, let's understand the terminology.
A chromosome is a structural element of the cell nucleus in which genes are located. The name “chromosome” in Greek means “painted body”. Most likely, due to the fact that during cell division - mitosis or meiosis, the chromosomes are stained in different colors.
One of the first who decided to do the counting of chromosomes, was T. Painter. And because of his random error, the whole world for a long time thought that man has 48 of them. So how many chromosomes really are?
An error in the study found A. Levan and Joe Tio only 30 years after Painter. As it turned out, a healthy person has 23 pairs of chromosomes, which means that it is 46! chromosomes. Each chromosome has one DNA molecule, which includes 727 genes, each of which is responsible for a specific trait, and this is 60 million nucleotides, and only 2% of the human gene code. By the way, there are some differences in the number of chromosomes in different cells.
How many chromosomes in human cells
Somatic cells, which are larger in the body, are doubled or, in scientific terms, a diploid set of chromosomes. But in the composition of the germ cells, only a single set of chromosomes, because during fertilization, the female and male cells merge, as a result of which a double set is formed.
The biologist was important to know how many chromosomes in a healthy person, not only for the sake of interest, but also because of genetic disorders, which for a long time were considered psychiatric. And they arise as a result of the failure of chromosome division, gene mutation, as a result of which genetic diseases appear in humans.
The most frequent chromosomal mutations
The most common occurrence of an extra chromosome, the so-called trisomy or tetrasomy. These violations result in Down syndrome, Kleinfelter syndrome and other incurable diseases.
Down's disease occurs due to the addition of an extra chromosome to the pair. The syndrome is quite easy to recognize. Already from birth, the baby's face looks flat, excessively large, there is a skin fold in the neck. Muscles have low tone.Such people tend to live quite a bit. They suffer from the intellect and the social sphere of life;
Kleinfelter disease occurs when one or more additional chromosomes are added to a pair. A person with this disease can be distinguished by the violation of the proportions of the body. In men, there is the female breast, and excessively long limbs. Also, patients have complete sterility and difficulty with mental operations;
In addition, the well-known and other syndromes of Patau and Edwards syndrome. In people with this disease, trisomy occurs on chromosome 13 and 18, respectively. Children with such disorders do not live even up to a year.
Genetic disorders are diagnosed before birth. No one is immune from these diseases, but it has been proven that children with similar syndromes are born more often in dysfunctional families.
Modern medicine can determine how many chromosomes a person has before the birth of him, which allows him to closely monitor the development of the fetus.