fluorescence in situ hybridization (floor-EH-sents in SY-too HY-brih-dih-ZAY-shun)
A technique used to look at chromosomes (the parts of the cell that contain genetic information in the form of DNA) or genes (specific regions of DNA in chromosomes that make RNA and proteins). Pieces of DNA containing a fluorescent dye are made in the laboratory and added to cells on a glass slide. When viewed under a microscope with a special light source, parts of chromosomes or genes that bind the pieces of DNA show up as colored. Also called FISH.