The mysteries of the fifteenth chromosome

Igor Eruandovich Lalayants, Ng.ruA "site" of anxiety has been found in the human genome

James Watson, the discoverer of the DNA double helix, in his latest book, or rather even during one of the interviews given at its presentation, rather unexpectedly stated, rejecting any political correctness, that the African race has different genes of mind than the whites.

He was of course referring to the molecular features that characterize "intelligent" genes.

Outraged critics rejected the subtleties of the differences between the deank sequences that they did not understand and concentrated on the "racism" of the patriarch of the study of the human genome. But was it really worth it to revile the venerable elder, who does not suffer from senile senility at all. After all, in another section of the interview, he proudly stated that a small fraction of Negro blood also flows in his veins. And who in the USA does not have it! It's just like Karamzin, who said to himself that scratch every Russian and you will immediately find a Tatar… Perhaps it would be necessary to delve deeper into the causes of genetic differences. Moreover, modern methods of studying genetic material supply an abundance of information for reflection. There is also a special scientific term for describing the differences indicated by Watson – retardancy.

Retardancy is a lag in the mental development of a child, which can occur for a thousand reasons. In the last few years, several genes have been isolated, mutations of which lead to certain disorders in the development of the brain. There is a gene whose disorders lead to microgyria, or grinding of the gyrus. With a mutation in another gene, a child is born with microcephaly, that is, a head reduced in size and, accordingly, an undeveloped brain. There are autism genes, and there is a speech gene – with violations in its structure, a child does not develop normal speech, although this does not affect mental abilities in any way…

And here is a new discovery, the message of which is published in the February issue of the journal Nature Genetics. An international group of scientists led by Evan Eikler from the University. Washington analyzed DNA samples from more than two thousand patients from the UK and Italy suffering from mental retardation, seizures and some other neurological disorders. The attention of scientists was drawn primarily to a certain section of the 15th human chromosome, in which several patients showed giant deficiencies (deletions) of the "letters" of the gene code, that is, a fragment of the substance of life was missing. These deletions reached one million nucleotides (megabases).

All of them had mental underdevelopment in combination with epilepsy or abnormal brain activity. These symptoms were combined with inverted full lips and abnormalities in the development of fingers and hands. Genetic tests of more than two thousand healthy individuals did not reveal any abnormalities or deletions in this section of the 15th chromosome.

The new discovery confirms the earlier conclusions of scientists who have long noted the presence of a "site" of anxiety in the 15th chromosome. DNA segments can perform inversions – turn in the opposite direction, which leads to such anomalies as Prader-Willi and Angelman syndromes. The new isolated site contains six genes, mutations of one of which leads to the development of convulsive disorders.

Eikler tried to explain the mechanism of the occurrence of deank mutations from the standpoint of human molecular evolution: "This site is literally stuffed with DNA sequence duplications that have accumulated over 10-15 million years of human evolution as an intelligent being. We do not yet understand the reason for this not entirely clear process, but its result is the emergence of a section of the genome in which rearrangements-rearrangements are very common and can have great consequences."

A new form of mental retardation, the development of which is based on deletions of the DNA section of the 15th chromosome, occurs only in three cases per thousand people with intellectual underdevelopment. However, Eikler believes that this is an extremely low estimate. It is quite possible that we are talking about 15-20% of the total number of cases of mental retardation. This circumstance will make it economically advantageous to identify specific molecular mechanisms of nerve tissue damage and the development of drugs. Eikler also foresees that understanding the causes of "deletion" mental retardation will allow for a more targeted search for mechanisms and other forms of it.

It remains to find the means to conduct an even larger study of at least 7,500 patients in order to identify not only the most common re-arrangements, but also the more rare ones. It is interesting to see the state of this region of the 15th chromosome in a fairly large number of Africans, who are the most ancient race with the fewest initial gene mutations. It is known that the ancestors of modern man migrated from Africa and during their settlement around the world accumulated much more changes in their genes than representatives of the "original" Africans.

Portal "Eternal youth" www.vechnayamolodost.ru 23.04.2008