PRECISE MAPPING OF A DENOVO DUPLICATION 18(Q21-]Q22) UTILIZING CYTOGENETIC, BIOCHEMICAL, AND MOLECULAR TECHNIQUES

We describe the first de novo inverted duplication of 18q. Due to the difficulty of identifying de novo chromosome abnormalities based solel y on cytologic studies, precise definition of the 18q duplication was attempted by integrating cytogenetic and clinical findings with bioche mical and molecular dosage studies. The combined results demonstrated that the proposita had a duplication of 18q21-->q22 with a karyotype o f 46,XX, - 18, + inv dup(18) (pter-->q12.1=q22-->q21=q12.1-->qter). Th e duplication of this specific chromosome region does not result in th e typical 18 phenotype, supporting the hypothesis that various loci on chromosome 18 may interact to produce the manifestations of this synd rome.