Abstract
A method is presented for the extraction of deoxyribonucleic acid from thin sections of tissue fixed in glutaraldehyde and osmium tetroxide and embedded in water-insoluble epoxy resin. Incubation of thin sections in 20% perchloric acid at 60°C for 8 hr produced electron-transparent bands in the polytene chromosomes from Drosophila salivary glands. Chromosome bands were also rendered electron-transparent when hydroxypropylmethacrylate-embedded thin sections were digested with deoxyribonuclease or extracted with perchloric acid. Nucleolar ribonucleic acid was unaffected by the perchloric acid extraction.