Distribution of H3K4me3 across human metaphase chromosomes. (a-c) Metaphase chromosome spreads from human lymphoblastoid cells immunostained with antibodies to H3K4me3 (fluorescein isothiocyanate (FITC), green) and counterstained with DAPI (pseudocolored red). Panel (a) shows both stains, panel (b) FITC only and panel (c) DAPI only, shown in black to resemble conventional G-banding. (d) Immunostained karyotype constructed from the chromosome spread shown in (a-c). (e) Reverse DAPI (rDAPI) karyotype constructed from the same spread.