In December 1969, Lore Zech at the Karolinska Institute in Stockholm first reported intense fluorescence of the A T-rich distal half of the long arm of the Y chromosome in the nuclei of metaphase cells treated with quinacrine mustard. In April 1970, Peter Pearson and Martin Bobrow at the MRC Population Genetics Unit in Oxford and Canino Vosa at the University of Oxford reported fluorescent "male" sex chromatin bodies in the nuclei of interphase cells in buccal smears treated with quinacrine dihydrochloride, which could be used to screen for Y chromosome aneuploidies like 47,XYY.