Because autism is strongly genetic, and boys and girls share the vast majority of their genomes, the disorder's male bias is puzzling. No common risk or protective factors have yet been identified on the sex chromosomes that could account for the dramatic difference in prevalence between the sexes. Dr. Weiss and her colleagues are trying to uncover the genetic causes for sexual dimorphism in autism. Most autism studies to date have included a ratio of male to female participants that reflects the disorder's prevalence — meaning there are not enough female participants to make robust sex comparisons. Weiss' team plans to recruit additional female participants to boost the statistical power of other autism genetic repositories, such as the Simons Simplex Collection and the Autism Genetic Resource Exchange (AGRE). The researchers will use microarray technology to comb these samples for variations in DNA sequence and gene copy number across the participants' genomes. The team will then compare these variations between males and females to prove or disprove the various genetic theories and identify sex-specific susceptibility genes. Determining what protects girls from autism will be useful in understanding, and potentially reducing, the risk for boys.