FRAGILE SITE AND INTERSTITIAL TELOMERE REPEAT SEQUENCES AT THE FUSIONPOINT OF A DE-NOVO (Y-13) TRANSLOCATION

We describe a novel fragile site in a rearranged chromosome, associate d with the presence of telomeric repeat sequences at the fusion point of a translocation between chromosomes 13 and Y. The case reported in this study shows a de novo (Y;13) translocation, which appears to repr esent fusion of an apparently intact chromosome Y with a chromosome 13 that has lost only part of its short arm. Ten percent of the cells sh ow a normal karyotype without the (Y;13) translocation. Molecular cyto genetic studies of the derived Y;13 chromosome revealed three hybridiz ation sites of the telomeric probes - one at each end and one at the b reakpoint junction. A fragile site is also observed in the intrachromo somic telomeric region. This coincidence suggests that the telomere re peat sequences (TTAGGG)n, when present at an interstitial chromosomal location, can promote the formation of a novel fragile site.