HIGH-RESOLUTION MAPPING OF INTERSTITIAL LONG ARM DELETIONS OF CHROMOSOME-16 - RELATIONSHIP TO PHENOTYPE

The breakpoints of seven interstitial deletions of the long arm of chr omosome 16 and two ring chromosomes of this chromosome were mapped by in situ hybridisation or by analysis of mouse/human somatic cell hybri ds containing the deleted chromosome 16. Use of a high resolution cyto genetic based physical map of chromosome 16 enabled breakpoints to be assigned to an average resolution of at least 1.6 Mb. In general, inte rstitial deletions involving q12 or q22.1 have broadly similar phenoty pes though there are differences in specific abnormalities. Deletions involving regions more distal, from 16q22.1 to 16q24.1, were associate d with relatively mild dysmorphism. One region of the long arm, q24.2 to q24.3, was not involved in any deletion, either in this study or in any previous report. Presumably, monosomy for this region is lethal. In contrast, patients with deletions of 16q21 have a normal phenotype. These results are consistent with the proposed distribution of genes, frequent in telomeric Giesma light band regions but infrequent in G p ositive bands.