Over the last several years, dramatic advances have emerged from the study of copy number variants (CNVs) such as submicroscopic chromosomal deletions and duplications (Iafrate et al., 2004; Sebat et al., 2004). Sebat et al. (2007) first noted that “large” (mean size of 2.3Mb), rare (<1% frequency in the general population), de novo events were more frequent in ASD probands from families with only a single affected child (i.e. simplex families) than in controls, as well as in comparison to probands from families with more than one affected individual (i.e. multiplex families).
