The purity and integrity of Isolated RNA IS a critical determinant of its effectiveness in such molecular biological procedures as Northern blot, poly A+ RNA separation, cDNA synthesis, and in vitro transcription and translation The successful isolation of total RNA from tissues or cell lines by any procedure involves four major steps: complete disruption of the cells or tissues; effective denaturation of the nuclear protein complex; inactivation of endogenous ribonuclease (RNase) activity; and purification of the RNA from the contaminating DNA, protein, and carbohydrates.