Their study, known as the Autism Genome Project (AGP), was conducted in two stages. The first stage of consisted of a genome-wide association study using genetic data from 1400 families affected by autism; the second stage checked the associations discovered in the first stage using the genetic data from an additional 1301 ASD-affected families and included another new genome-wide association study which combined the study subjects from both stages.
When all the analyses were said and done, no SNPs (common genetic variations) were significantly associated with ASD. Furthermore, when some of the SNPs that had been identified in the first study as possibly associated with ASD were tested in the second-stage families, the associations failed to hold up. This lack of common SNPs associated with ASD is both disappointing and enlightening.
Knowledge of what is not true, paradoxically, is knowledge of what is true. For instance, if I tell you that my pet Tyger is not a dog, you are one step closer to knowing Tyger’s a cat. Most of science progresses through “not trues” — the failed hypotheses that bring us closer to real understanding. A perfect example of this mode of scientific progress is this recent genetic study. Their lack of findings was quite a finding.