FLUORESCENCE IN-SITU HYBRIDIZATION REVEALS A BREAK IN THE ALPHA-SATELLITE DNA OF CHROMOSOME-1 IN A FAMILY WITH A BALANCED WHOLE-ARM TRANSLOCATION

We have characterized a whole-arm translocation involving chromosomes 1 and 19 by traditional cytogenetic methods and fluorescence in situ h ybridization with chromosome-specific alpha-satellite and whole-chromo some painting probes, and different satellite III DNA probes. We have identified a break in the alpha-satellite DNA region of chromosome 1, with division of this material into two alpha-satellite DNA blocks. Th is leaves one translocation chromosome with truncated alpha-satellite DNA from chromosome 1 and the other trranslocation chromosome with all the alpha-satellite DNA from chromosome 19 and truncated alpha-satell ite DNA from chromosome 1. We speculate whether the recombination even t observed has taken place in tetraplex structures of satellite III DN A interspersed between alpha-satellite DNA.