Optimum pH for nuclear sex identification using quinacrine.

Preparations of quinacrine stained interphase nuclei from buccal smears and hair root sheaths were mounted in MacIlvaine's buffer at various pH's in an attempt to obtain optimum differentiation of X- and Y-chromatin. Relatively high pH (5-8) was associated with intense nuclear fluorescence. Background nuclear fluorescence decreased with lower pH's (2-4), revealing distinct granules. X-chromatin is best differentiated against this decreased background, while positive identification of Y-chromatin is more certain in the absence of confusing granules. Hence optimum pH for X-chromatin screening in quinacrine stained preparations is approximately 3.0, that for Y-chromatin screening 5.5.