Is the childs IQ inherited from mother or father?

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 Is the childs IQ inherited from mother or father?


But is the saying that intelligence gene is on the X chromosome is really groundless?

Is intelligence gene on X chromosome?

In fact, as early as 1972, some people in the scientific community put forward the idea that intelligence gene is on the X chromosome. At that time, gene sequencing had not yet been realized, and the researchers only made this guess based on statistical differences in IQ between men and women. Because they found that although the statistical distribution of IQ of men and women is Gaussian distribution, the variance of IQ distribution of men is larger, that is to say, the proportion of men with extremely high and low IQ is higher than that of women. It seems that there is not only a close genetic relationship between mental retardation and mental retardation. This conjecture was gradually confirmed by experiments.

At the beginning of this century, with the vigorous development of human genome project, more and more gene sequence codes have been cracked. Scientists have found that at least 40% of the nearly 1000 protein coding genes on the X chromosome are expressed in the brain, which is higher than that on the autosomal chromosome and far more than on the Y chromosome. In other words, X chromosome has a great effect on brain structure, cognitive ability, intellectual development and so on. For boys, their only X chromosome comes from their mother. In other words, theoretically speaking, the genetic effect of mother on sons intelligence should be huge, but why is there no significant correlation between IQ statistics? What is the matter?

How do genes on the X chromosome determine brain structure?

This involves two concepts: X-inactivation and chromosome recombination in meiosis.

For men, the task of compiling the genes for the brain structure on the X chromosome is simple, because there is only one gene, just use it. For women, they have two sets of X chromosomes, and if both sets are used to express proteins, then they are confused. So choosing which one to compile the brain becomes a problem. In a womans cell, one of the two sets of X staining will automatically lose its activity, leaving only one set of decoded and encoded proteins. This phenomenon of inactivation of one of the two X chromosomes is called X chromosome inactivation. It is generally believed that in most cases during the development of female embryos, the process of which set of X chromosome inactivation is selected from different cells is random. As a result, about half of the embryo cells come from the mothers X chromosome inactivation, while the other half comes from the fathers X chromosome inactivation. So when the gene compiles the brain structure, at one time it comes from the mothers X chromosome, while the other comes from the fathers role. There is no fixed pattern, and the X chromosome gene expression is fully mixed. In addition, there are about 15% genes in human X chromosome that can escape the disaster of inactivation, which makes the compilation of X chromosome very complicated.

On the other hand, meiosis is a special way of cell division. When a sex cell divides, the chromosome is duplicated only once, and the cell divides twice in succession. In this way, the number of chromosomes in the cell is halved. Women have two X chromosomes, one X in each egg cell during meiosis. When a cell divides continuously, chromosomes will be recombined many times. Two different x staining from parents will exchange some genes in the same position, which will make the X chromosome of each egg cell mixed with the genes of the original two X chromosomes.

So, when the son got the X chromosome from his mother, it was the result of meiosis and chromosome recombination, a mixture of X chromosomes from his grandparents. The X chromosome used by his mother when compiling the brain was also randomly selected. The brain structure of mother and son may be completely different, or there may be a great degree of similarity. The most likely result is that there are some similarities and some differences. The design of nature is so ingenious. Although the mother should take the main responsibility for the genetic problem of sons intelligence, the intelligence level of his son can not be predicted by the intelligence of his mother.

In addition, due to the existence of genomic imprinting, some scientists speculate that, compared with mothers who inherit intelligence through X chromosome, fathers express genes through autosomal, thus affecting the brain and behavior of their offspring. However, because gene imprinting is rare, accounting for less than 1%, this effect is not significant.

The evolution of human intelligence and genius gene

Many scientists also speculate that genius genes are also closely related to the X chromosome. The picture below represents such a simple model of the emergence and spread of gifted genes. There are only six genes in this model, all on the X chromosome. After meiosis on the X chromosome, the first generation of mothers produced a gifted gene combination, the son of all a gene. This son married another woman and had two children, and his genius genes could only be passed on to his daughter, not to his son. But his daughter remarried, because of the chromosome recombination (x position) in meiosis, the genius gene combination was broken up, all the fourth generation were mediocre, but the gene was still spreading, looking forward to the opportunity of the genius combination again. So, although the gene of genius can continue, the emergence of genius is just an accident. If it is true that the gene of genius still needs to be inherited by daughters, then all talented men should have daughters. Otherwise, if the genes are broken in their sons, what a great loss to human beings. Source: observer.com editor in charge: Wu Yanli_ NBJS6202

Many scientists also speculate that genius genes are also closely related to the X chromosome. The picture below represents such a simple model of the emergence and spread of gifted genes. There are only six genes in this model, all on the X chromosome. After meiosis on the X chromosome, the first generation of mothers produced a gifted gene combination, the son of all a gene. This son married another woman and had two children, and his genius genes could only be passed on to his daughter, not to his son. But his daughter remarried, because of the chromosome recombination (x position) in meiosis, the genius gene combination was broken up, all the fourth generation were mediocre, but the gene was still spreading, looking forward to the opportunity of the genius combination again. So, although the gene of genius can continue, the emergence of genius is just an accident.