Genes and intelligence: new data
Scientists have found a gene mutation in which lowers IQ by 25 points
"The intellectual abilities of each person are the sum of many elements, most of which are genetic in nature and inherited from parents. Each direct relative has 50% of your genetic code, and accordingly, these 50% determine about the same proportion of your intelligence," said Sebastian Jacquemont from the University of Lausanne (in a press release from the Université de Montréal Twenty–five-point drop in IQ caused by lack of gene copy – VM).
Guided by this idea, Jacquemont and his colleagues have been searching for several years for genes and mutations associated with the development of autism, schizophrenia and other brain problems that are associated with a decrease in intellectual abilities. Scientists find similar "typos" in DNA by comparing the DNA structure of members of the same family suffering from autism and schizophrenia with the genome structure of people from the control group.
Relatively recently, scientists have discovered that an unusual mutation in chromosome 16, known as "duplication 16p11.2", leads to the development of a number of syndromes associated with impaired consciousness – it is often found among autistics and schizophrenics, and also makes a person more susceptible to malnutrition and anorexia.
The authors of the article decided to check how the appearance of additional copies of this section of chromosome 16 affects a person's intellectual abilities. To do this, they gathered a group of thousands of volunteers, about two hundred of whom had either one or two extra copies of 16p11.2, and asked them to take a series of tests to determine IQ and the degree of development of autism.
As this experiment showed, the presence of two additional copies of 16p11.2 was associated with serious intellectual development disorders – carriers of such mutations on average had an IQ 25 points lower than people without such mutations, and 16 points lower than their relatives who had only one such extra copy. The removal of one of the normal copies of 16p11.2 led to similar consequences, which caused a similar drop in IQ level.
In addition to a decrease in intelligence, the appearance of additional copies of 16p11.2 was associated with increased susceptibility to epilepsy and the development of various disorders and deformities in the structure of the brain and blood vessels of the head. In addition, carriers of these mutations later began to walk and, in general, more often suffered from mental disorders.
Such a sharp drop in IQ actually transfers the owners of this mutation from the category of normal people, whose IQ is approximately 100-105 points, to the category of mentally retarded persons, whose IQ often approached the 65-70 point mark. Further study of 16p11.2, as the authors of the article hope, will help to understand whether it is possible to deal with such disorders and how doctors can help children with similar genetic defects not to lag behind in development.
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28.01.2015