The field of molecular cytogenetics is presently hampered by the need for allele- and homologue-specific hybridization probes. Vast stretches of the human genome display a considerable amount of polymorphic variation between individuals. Alpha satellite DNA is a tandemly repeated sequence located at the centromeres of all primate chromosomes and is a rich source of polymorphisms. These DNA variants are phenotypically silent; they are also stable and heritable in Mendelian fashion. We have shown that we can use this genetic diversity to create homologue-specific probes using fluorescence in situ hybridization (FISH) However unlike most classical heteromorphisms, which are detected by banding techniques, our approach does not depend upon detection of gross alterations in chromosome structure, but on the basis of sequence composition. We have constructed highly-specific oligonucleotide probes that are the first reported FISH probes to discriminate between the cytogenetically indistinguishable chromosomes of normal individuals.
These sequence-specific probes have been used to follow the transmission of a single chromosome 17 through three generation families, similar to a typical polymorphic marker.