Cytogenetic Technology — Genotype and Phenotype

In this issue of the Journal, Mefford et al.1 describe an association between a microdeletion at 1q21.1 and a diverse range of impairments: mental retardation associated with microcephaly, cardiac abnormalities, or cataracts. A microdeletion at 16p11.2, causing autism or mental retardation, was reported earlier this year in the Journal.2 These discoveries were made possible by a technologic revolution in human cytogenetics: genomewide assessment of copy-number alterations (deletions and duplications) by means of high-density array technologies, hereafter referred to as cytogenetic arrays.35 The resultant proliferation of new cytogenetic syndromes is reminiscent of an earlier era in human cytogenetics: “During . . .