The need to combine chromosome banding with fluorescence in situ hybridization has meant that banding techniques using fluorescent dyes has become more popular. Q-banding involves staining with quinacrine which reacts specifically with certain bases. Quinacrine intercalates into chromosomal DNA irrespective of sequence, but fluoresces brighter in regions of AT-rich DNA. There are a number of other molecules whose fluorescence is influenced by the base composition of the DNA to which they are bound. In addition to quinacrine, other commonly used fluorochromes with a specificity for AT-rich DNA include Hoechst 33258, DAPI (4’-6diamidino-2-phenylindole) and daunomycin. The fluorescence of Hoechst and DAPI is not quenched by guanine andsotheygivelessdistinctbandsthanthoseproducedby quinacrine; however, daunomycin fluorescence is greatly quenched by DNA with a GC content of 432%. DAPI staininghastheadvantagethatitisvery resistanttofading andthatitsexcitationandemission spectraare compatible withreportermoleculesandfilterscommonlyusedinFISH