Does anyone know where autism comes from --genes?

Multiple Factors: There are some know genetic causes of autism - the most common of these is fragile x syndrome. However, many childrent with autism have no known genetic problem. Genetic difficulties play a role, but there are other environmental factors that are suspected to play a role as well, such as environmental toxins and even the possbility of viral illnesses. Obviously, there is still much to learn.

Genetic testing: For autism &/or intellectual disability is comparative genomic hybridization to detect copy errors in a tiny bit, 250 base pairs of dna. Instead of having one bit from dad's dna & one from mom, the person got 2+1 or 1+0. Other factors, like some viruses during pregnancy, can change the expression of a gene in the fetus.Environmental factors may cause gene expression in a child, also.