Improved autoradiographic procedure for cytogenetics: inverted coverslips and double illumination.

The method described here has the advantage of presenting a clear image of both chromosomes and silver grains. Chromosomes are stained through the emulsion with Hoechst 33258. As two different sources of light are employed-epi-ultraviolet illumination and transmitted visible light-a separate photographic record of each optical plane can be obtained of chromosomes, silver grains, and chromosomes and grains together.