Demonstration of spontaneous XX/XY chimerism by DNA fingerprinting.

The M13 bacteriophage probe, which makes possible the establishment of DNA fingerprints, was used to study a phenotypically normal woman with a 46XY karyotype and her twin brother. Identical fingerprints and positive hybridization with a series of Y-specific probes were obtained on blood samples from the siblings. DNA from a skin biopsy of the woman yielded a clearly different pattern and displayed no Y-specific hybridization, indicating that she is a spontaneous chimera. This study illustrates the use of DNA fingerprinting as a powerful and simple aid to the diagnosis of natural chimerism.