ScienceDaily (June 10, 2010) — The world's largest DNA scan for familial autism has uncovered new genetic changes in autistic children that are often not present in their parents. Identified in less than 1 percent of the population, these rare variants occur nearly 20 percent more in autistic children.
Using blood samples from 996 elementary school-age children diagnosed on the autism spectrum from the United States, Canada, and Europe, the scientific teams combed the children's DNA for rare deletions and duplications. In particular, they hunted for changes in the genetic information that a child inherits from each parent. The families consisted of parents with one autistic child.
"We discovered two striking things. First, the rare variants interfered nearly 20 percent more in the genes of autistic children than in the healthy children," said Dr. Daniel Geschwind, Gordon and Virginia MacDonald Distinguished Chair in Human Genetics and UCLA professor of neurology and psychiatry. "Second, we found a number of disruptions that are new, or de novo. The autistic child is the first in their family to carry that variant. The parents do not have it.
"This suggests that tiny genetic errors may occur during formation of the parents' eggs and sperm, and these variations are copied during creation of their child's DNA," added Geschwind, who is also director of the UCLA Center for Autism Research and Treatment. "The finding parallels what takes place in chromosomal disorders like Down's syndrome."
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