The study focuses on spontaneous mutations, not inherited gene glitches that are handed down from parent to child.
Such spontaneous mutations may affect 100 or more different genes and appear to be "frequent" with autism, researcher Jonathan Sebat, PhD, tells WebMD.
By screening for such mutations, "we may be able to inform parents about their risk for having a second child with autism," says Sebat, who works at Cold Spring Harbor Laboratory in Cold Spring, N.Y.
The study appears online in Science Express.
Autism Gene Study
Sebat's team studied 264 families, not all of which had an autistic child.
Of the families studied, 118 families had one child with an autism spectrum disorder, 47 families had multiple children with an autism spectrum disorder, and 99 families had no diagnoses of autism spectrum disorders.
The scientists looked for chunks of DNA that were duplicated or deleted. They also checked whether those gene glitches were spontaneous mutations, which weren't passed down from parent to child.
Spontaneous DNA mutations were seen in more than 10% of the autistic participants studied, Sebat tells WebMD.
The mutations were typically deletions, not duplications, of DNA chunks.
The mutations didn't just turn up in one or two genes. Instead, they were found at many locations throughout the genome, and the mutations weren't the same in every patient.
Some mutations involved more than one gene. For instance, one child with an autism spectrum disorder had a DNA deletion that involved approximately 27 genes, the study shows.
All in all, the researchers spotted 17 spontaneous mutations in 16 participants, 14 of whom had an autism spectrum disorder.
More Than 100 Autism Genes?
"These data are consistent with the hypothesis that there are many autism genes in the genome," Sebat tells WebMD.
He speculates that there could be "100 or more" autism genes.
The spontaneous gene mutations were typically seen in families with only one autistic child. The genetics of autism may unfold differently in families with several autistic children, Sebat notes.