2. genotyping single nucleotide polymorphisms (SNPs) across the deleted genomic region. Genotyping will be performed using approximately 75 previously characterized SNPs, with an increased density of SNPs in the target candidate genes (~3-5 SNPs per candidate gene). In order to determine whether a haplotype and/or variants of genes within region 22q11.2 contribute to the autistic phenotype and related neuro-psychological impairments in patients with the deletion, we will identify DNA polymorphisms using existing databases. We will then genotype patients with the 22q11.2 deletion for the selected polymorphisms and compare the allele frequencies and haplotype combinations in 22q11DS patients with the phenotype (“cases”) to those deleted patients without these findings (“controls”) applying chi-square, Fisher’s exact test, and other statistical genetic methods as appropriate.