Fluorescent in situ hybridization assessment of chromosome copy number in buccal mucosal cells.

Sex chromatin (Barr body) analysis of buccal mucosal cells has been recognized for many years as an inexpensive, noninvasive and rapid means of sex determination. The conventional Barr body analysis using Papanicolaou stain was discontinued as a routine test because of its lack of reliability and its inability to detect mosaicism and other chromosomal abnormalities. With the advent of recombinant DNA technology and the availability of molecular probes, however, the value of this simple albeit obsolete test should be re-evaluated. The results of the authors' experience in optimizing a fluorescent in situ hybridization (FISH) assay on buccal mucosal cells are described. The utility and potential of this assay are explored and discussed.