Advances in whole-genome genetic testing: from chromosomes to microarrays.

Whole-genome genetic diagnostics has changed the clinical landscape of pediatric and adolescent medicine. In this article, we review the history of clinical cytogenetics as the field has progressed from studying chromosomes prepared from cells squashed between 2 slides to the high-resolution, whole-genome technology in use today, which has allowed for the identification of numerous previously unrecognized microdeletion and microduplication syndromes. Types of arrays and the data they collect are addressed, as are the types of results that array comparative genomic hybridization studies may generate. Throughout the review, we present case stories to illustrate the familiar (Down syndrome) and the new (a never-before reported microdeletion on the long arm of chromosome 12).