Isolation of deoxyribonucleic acid from mammalian tissues.

1. DNA has been isolated from different mammalian tissues. The DNA preparations were free from RNA, protein and polysaccharides and have a similar range of sedimentation coefficients (approx. 24s). 2. Protein was removed by a two-stage extraction with a phenol–cresol mixture by using a detergent with 4-aminosalicylate in the first stage and sodium chloride in the second. 3. Polysaccharides remained in solution when DNA was precipitated with 2-butoxyethanol in the presence of 0·5m-sodium chloride and 1·5m-sodium benzoate. 4. Ribosomal RNA was removed by precipitation in the presence of 3m-sodium chloride at 0°, when DNA remained soluble.