Clonal Origin of the Philadelphia Chromosome From Either the Paternal or the Maternal Chromosome Number 22

The heteromorphic regions of chromosome 22 were studied with the quinacrine mustard fluorescence technique in eight patients with Philadelphia chromosome-positive chronic myelocytic leukemia and in their parents. The fluorescence pattern showed that the Philadelphia chromosome had originated from the paternal chromosome 22 in one case and the maternal in another. The other six cases were noninformative in this respect. The fluorescence pattern was consistent between cells in both the informative cases. These results speak in favor of a clonal origin of the Philadelphia chromosome from either the paternal or the maternal chromosome 22.