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 hybridization with chromosome-specific alpha-satellite and whole-chromosome 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. This leaves one translocation chromosome with truncated alpha-satellite DNA from chromosome 1 and the other translocation chromosome with all the alpha-satellite DNA from chromosome 19 and truncated alpha-satellite DNA from chromosome 1. We speculate whether the recombination event observed has taken place in tetraplex structures of satellite III DNA interspersed between alpha-satellite DNA.