Purification of total cellular DNA from a single plant

A procedure is outlined for purifying DNA from a single plant. A crude organelle pellet consisting of nuclei, chromatin, chloroplasts, and mitochondria is prepared, suspended, and immediately lysed with detergents. The DNA is separated from RNA, protein, and polysaccharides by banding it in CsCl density equilibrium gradients. Ethidium bromide is included in all buffers to act as an inhibitor of DNAase activity. The DNA prepared in this manner can be digested with restriction endonucleases, separated by gel electrophoresis, and used to identify specific genes by hybridization of cloned DNA sequences.