Differential destabilization of repetitive sequence hybrids in fluorescence in situ hybridization

A method for painting a chromosome or chromosome region by fluorescence in situ hybridization (FISH) without blocking DNA is described. Both unique se quence and repetitive sequence components of a fluorescently labeled probe are hybridized under low-stringency conditions, but the chromosomes are was hed in such a manner that repetitive sequences are differentially removed, while region-specific unique sequence fragments remain bound to the target chromosomes. We refer to this differential retention and removal of probe c omponents as differential stability FISH.