The same gene family that may have helped the human brain become larger and more complex than in any other animal also is linked to the severity of autism. The gene family is made up of over 270 copies of a segment of DNA called DUF1220. DUF1220 codes for a protein domain -- a specific functionally important segment within a protein. The more copies of a specific DUF1220 subtype a person with autism has, the more severe the symptoms, according to a new paper.