Why do people have exactly 23 pairs of chromosomes?

Another of the course the school of biology, we know that in the normal formation of the human body (ie: without a variety of birth defects), a large part of our genetic information is encoded in the 23 pairs of chromosomes. But have you ever wondered why these couples is 23? Why not 24, 25 or even 16? And indeed, why it is an even number of chromosomes? Let's investigate.

Why do people have exactly 23 pairs of chromosomes?

DNA and chromosomes

To understand what a chromosome, you must first understand what DNA. DNA is a complex molecule occurring in all plants and animals. It is contained in almost every cell in the body and carries with it all the information necessary to maintain the life of the organism, providing all internal processes and, most importantly, for reproduction. DNA is the primary mode of transmission of the genetic information in the reproduction process part of the DNA is transmitted from both parents to offspring.

See also: CRISPR helped to create a new look with a giant chromosome

Such a huge amount of information carried by our DNA, must consume a lot of "space". And indeed it is. If the "stretch" DNA contained in only one cell, then its length is about 2 meters. And our body is quite a clever system of packaging of all this amount of data. And this helps just chromosome.

Why are 23 pairs of chromosomes

Immediately it should be noted that the number in the 23 pairs of chromosomes is not universal among living beings. Firstly, people are "diploid" species, which means that most of our chromosomes form matched pairs (though there are species in which an odd number of chromosomes). This simplifies the storage of information. However, the complexity of the type of organization does not depend on the number of pairs of chromosomes. For example, some species of frogs, 18 pairs of chromosomes, while the shrimp 90 pairs!

Why do people have exactly 23 pairs of chromosomes?

Who would have thought, but this tiny species chromosome pairs more than the human

"People have 23 pairs of chromosomes, while the great apes (chimpanzees, gorillas and orangutans) have 24 pairs of chromosomes," - says the researcher at the National Research Institute of the human genome Belen Hurley. "This is due to the fact that the two chromosomes ancestral ape to human evolutionary lines were merged into one. Thus, a person on a single pair of chromosomes less. This is one of the main differences between the human genome and the genome of our closest relatives. We can say that this amount is due to historically. At the same time, it is undeniable that once the number of chromosomes in ancestors was another, but this set of genes not normally allow them to exist, and so the body "had to" evolve. "

What happens if the number of chromosomes change

Increase or decrease in the number of chromosomes in the adult organism can not practically occur. But it can happen in the formation of the fetus in the womb. One of the most common forms of pathology is trisomy of chromosomes, which lies in the presence of an extra chromosome in the cells. One well-known results trisomy is Down's syndrome, which is a condition caused by the presence of three (instead of two) in the chromosome 21 pair. The loss of one chromosome in a cell is called monosomy and describes a condition in which people have only one copy of a particular chromosome in the cell, rather than two.

In this case an odd number of chromosomes complicates the process of reading information or disrupt the operation of some systems (e.g., lack of sex chromosomes in a number of congenital diseases does not allow to have offspring). Thus, historically form the number 23 chromosome pairs allows us to live on this planet and to preserve the integrity of our species.

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