Phenol Extraction of Heavy Rapidly‐Labeled Nuclear RNA from Chick Embryos

Heavy rapidly‐labeled RNA from chick embryo nuclei separates on electrophoresis in 2.4% polyacrylamide gel into at least four fractions with the mobilities of rRNA precursors, and a fraction of “giant” RNA remaining at the start. The heavy fractions with mobilities of rRNA precursors pass into solution without heating during phenol treatment at pH 8.3 or during phenol‐1.6% dodecylsulphate treatment at pH 5. The “giant” RNA can be partially solubilized without heating by phenol‐1.6% dodecylsulphate treatment at pH 5 but the extraction becomes efficient only on heating to 65°C or on raising the pH to 8.3. Precautions are discussed to prevent the degradation of heavy RNA at elevated pH and the aggregation of rRNA at elevated temperature during phenol extraction.