Sau W. Cheung

Molecular cytogenetic evidence to characterize breakpoint regions in Robertsonian translocations

Four individuals carrying different Robertsonian translocations (13q;14q, 14q;21q, 14q;15q, and 13q;21q) were studied to determine the breakpoints involved in the generation of these derivative chromosomes. Sequential high-resolution G-banding, in situ hybridization using alphoid and ribosomal DNA probes, and C-banding were performed. In addition, silver staining was also used for visualization of the NOR region. The results provide direct molecular cytogenetic evidence that Robertsonian translocations can take place in different regions in both the short arm and proximal long arm of acrocentric chromosomes. Three different types of breakpoints were identified: between the ribosomal or alphoid sequences, as deduced from the banding and in situ hybridization results, and breaks in two seemingly unrelated regions on the two different chromosomes. The use of conventional cytogenetic techniques together with molecular studies allowed more precise evaluation of the breakpoints involved in Robertsonian translocations than either approach alone might have done.

High resolution R banding in amniotic fluid cells using the BrdU-Hoechst 33258-Giemsa (RBG) technique.

SummaryWhile standard Giemsa banding is generally adequate for amniotic fluid chromosome analysis, small deletions, duplications, or translocation breakpoints involving Gnegative bands may be difficult to appreciate. We report a method for producing high resolution R banding in human amniotic fluid cultures using the BrdU-Hoechst 33258-Giemsa (RBG) technique. RBG banding can be useful in confirming and precisely defining structural abnormalities in amniotic fluid cultures.