Autism Spectrum Disorders (ASD) are common genetic disorders, affecting approximately 1% of the population. In a small minority of individuals the disorder is associated with single gene disorders, such as Tuberous Sclerosis and Fragile X and occasionally ASDs co-occur with chromosomal abnormalities.

The single gene cause of autism have excited much debate about whether similar biochemical pathways might be implicated in the majority of affected individuals in whom the disorder is considered to occur on the basis of a complex genetic predisposition that is associated with extreme phenotypic variability. In this talk there will be a brief recap of basic molecular genetics and the principals underlying linkage and association strategies for gene identification will be outlined. The findings from linkage and association studies will be summarised and related to recently detected small changes in DNA sequence (Copy Number Variants). There is already some convergent evidence that genes coding for cell adhesion molecules might be implicated in autism and how these preliminary findings relate to the established neuropathology will be considered. The scope for including information from other family members will be explored and the implications of our current knowledge for genetic testing in clinical practise will be discussed.