Quinacrine Fluorescence for Identifying Metaphase Chromosomes, with Special Reference to Photomicrography

Metaphase chromosomes of humans and other species can be identified by their quinacrine fluorescence patterns. For the study of human chromosomes, standard phytohemagglutinin-stimulated leukocytes are used. A 45–60 min interval of colchicine treatment is used to obtain a higher proportion of extended chromosomes with contiguous chromatids which have generally proved to be most informative. Slides are stained with 0.5% quinacrine for 6 min, rinsed in running tap water for 3 min, and rinsed and mounted in a Tris-maleate buffer at pH 5.6. For photomicrography, a microscope with an HBO 200 w high-pressure mercury vapor lamp, 3 mm BG 12 excitor filter, darkfield condenser, fluorite 95x objective, K510 barrier filter and a nonautomatic exposure microphotographic attachment with an 8x eyepiece is used. With this system, images of adequate brightness reach the film plane, thus making possible the use of fine-grain, high definition 35 mm films, such as Kodak Panatomic-X and H & W Control VTE panchromatic. Photographic prints of moderately high contrast are used for preparing karyotypes in which every human chromosome can usually be readily identified.