The researchers involved in the Autism Genome Project searched for a special type of gene variant in which a whole DNA sequence is lost, or copied twice. These types of “broken” genes occur quite seldom, but have been known to appear in children with autism.
After comparing the DNA from 996 autistic people with that of 287 people without autism, the researchers found that people with autism had 19 percent more of the unusual gene variants on average.
Most significant, however, is the discovery that many of these “broken” gene sequences were only found among the autistic children themselves, not their parents. In short, the genes were newly created, and not inherited.
The authors of the study cannot say for certain when these defects occur, but they strongly suspect that they can be traced back to the time when parents’ eggs or sperm are first produced.
They conclude that the defects are small, genetic mistakes that occur spontaneously, and are intensely individual. Toxic substances in the environment could be involved in the mutation, according to a professor Christopher Gillberg, a Swedish researcher involved in the study.
“It will probably become clinically common that all children who have received a diagnosis of autism undergo a genetic examination,” Gillberg told TT.