Science 321, 218–223 (2008)

A pedigree analysis of 104 families has revealed associations between several genes and disorders in the spectrum that includes autism and Asperger syndrome.

Christopher Walsh of Harvard Medical School in Boston, Massachusetts, and his colleagues collected data from Middle Eastern families with affected members. Eighty-eight families in their sample had at least one child-bearing marriage between first cousins, which makes mapping genetic conditions simpler.

The analysis revealed several genomic regions that are linked to autism, including five large deletions. Several genes within these regions are thought to have a role in learning and seem to be important for stages of brain development during which autism symptoms usually develop.