Sequential Q- and Acridine orange-marker technique

A standardized Q- and acridine orange (AO)-fluorescence dual marker technique was described. It involved preservation of unstained chromosome slides in a vacuum desiccator up to 18 months, Q-staining, destaining, and treatment in Hanks' solution, pH 5.1, at 85 degrees C for 13 min, and acridine orange staining. Q-markers were found at the paracentromeric regions of chromosomes 3 and 4, the short arms and the satellites of the acrocentric chromosomes, while AO-marker spots were on the satellite-stalks of the acrocentrics. The advantage of the dual marker technique was illustrated by the determination of the origin of trisomy 22 in a spontaneous abortus.