Carrier RNA

Prepare a solution containing yeast tRNA (Boehringer Mannheim or Sigma) at a concentration of 10 mg/ml in sterile TE (pH 7.6), 0.1 M NaCl. Extract the solution twice with phenol (equilibrated in Tris-Cl at pH 7.6) and twice with chloroform. Precipitate the RNA with 2.5 volumes of ethanol at room temperature, and recover the RNA by centrifugation at 5000g (6500 rpm in a Sorvall SS-34 rotor) for 15 minutes at 4°C. Dissolve the pellet of RNA at a concentration of 10 mg/ml in sterile TE (pH 7.6). Store the carrier RNA in small aliquots at -20°C.