https://francais.medscape.com/voirarticle/3602026_4
https://ghr.nlm.nih.gov/condition/autism-spectrum-disorder#genes
What role do genes play?
Twin and family studies strongly suggest that some people have a genetic predisposition to autism. Identical twin studies show that if one twin is affected, then the other will be affected between 36 to 95 percent of the time. There are a number of studies in progress to determine the specific genetic factors associated with the development of ASD. In families with one child with ASD, the risk of having a second child with the disorder also increases. Many of the genes found to be associated with autism are involved in the function of the chemical connections between brain neurons (synapses). Researchers are looking for clues about which genes contribute to increased susceptibility. In some cases, parents and other relatives of a child with ASD show mild impairments in social communication skills or engage in repetitive behaviors. Evidence also suggests that emotional disorders such as bipolar disorder and schizophrenia occur more frequently than average in the families of people with ASD.
In addition to genetic variations that are inherited and are present in nearly all of a person’s cells, recent research has also shown that de novo, or spontaneous, gene mutations can influence the risk of developing autism spectrum disorder. De novo mutations are changes in sequences of deoxyribonucleic acid or DNA, the hereditary material in humans, which can occur spontaneously in a parent’s sperm or egg cell or during fertilization. The mutation then occurs in each cell as the fertilized egg divides. These mutations may affect single genes or they may be changes called copy number variations, in which stretches of DNA containing multiple genes are deleted or duplicated. Recent studies have shown that people with ASD tend to have more copy number de novo gene mutations than those without the disorder, suggesting that for some the risk of developing ASD is not the result of mutations in individual genes but rather spontaneous coding mutations across many genes. De novo mutations may explain genetic disorders in which an affected child has the mutation in each cell but the parents do not and there is no family pattern to the disorder. Autism risk also increases in children born to older parents. There is still much research to be done to determine the potential role of environmental factors on spontaneous mutations and how that influences ASD risk.
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