Contemplating effects of genomic structural variation.

Two developments have sparked new directions in the genetics-to-genomics transition for research and medical applications: the advance of whole-genome assays by array or DNA sequencing technologies, and the discovery among human genomes of extensive submicroscopic genomic structural variation, including copy number variation. For health care to benefit from interpretation of genomic data, we need to know how these variants contribute to the phenotype of the individual. Research is revealing the spectrum, both in size and complexity, of structural genotypic variation, and its association with a broad range of human phenotypes. Genomic disorders associated with relatively large, recurrent contiguous variants have been recognized for some time, as have certain Mendelian traits associated with functional disruption of single genes by structural variation. More recent examples from phenotype- and genotype-driven studies demonstrate a greater level of complexity, with evidence of incremental dosage effects, gene interaction networks, buffering and modifiers, and position effects. Mechanisms underlying such variation are emerging to provide a handle on the bulk of human variation, which is associated with complex traits and adaptive potential. Interpreting genotypes for personalized health care and communicating knowledge to the individual will be significant challenges for genomics professionals.