To read on the Examiner website:
Autism with intellectual disability shown to be inherited
Autism with intellectual disability (an IQ less than 70) was shown to be inherited by researchers from Brown University led by Eric Morrow, assistant professor of biology in the Department of Molecular Biology, Cell Biology, and Biochemistry at Brown University. The research was presented in the July 3, 2013, issue of the American Journal of Human Genetics.
Autism with intellectual disability is a small subset of the many disorders lumped together in the condition termed autism.
The scientists analyzing the DNA of more than 2,100 children with autism who were born into families where neither their parents nor a sibling has an autism disorder – a Simons Foundation data set known as the Simons Simplex Collection.
The researchers found that among the more than 500 children in the sample with autism and intellectual disability there were frequently more large runs of homozygosity than in their unaffected siblings.
Homozygosity means that the contributing genes from both parents have a much higher than “normal” similarity to each other. The condition of excessive homozygosity makes autism with intellectual disability a recessive genetic trait and explains the occurrence of the affliction in only one child in a family.
The work defining the genetic cause of autism with intellectual disability can also be used as a clinically useful biomarker for predicting the possibility that a child may be autistic with intellectual disability.
Homozygosity is rare due to the large number of potential mates in the world but the condition has its origin in the limited number of people that originally populated the Earth