Source and Description of Probe. A 1,486-bp rat cDNA clone for myogenin (MYOG) was excised from the EcoRI site of the plasmid, pBluescrybe M13- (Wright et al., 1989). Method of Detection. DNA was isolated from whole blood and digested with MspI. Fragments were then separated by agarose gel electrophoresis and transferred to charged nylon membranes. Hybridizations were at 65°C for 16 to 20 h (.5 M NaCl, .05 M Naphosphate buffer, pH 6.5, 5x Denhardt's reagent, 10% dextran sulfate, .5% SDS, 100 pg/mL sonicated, denatured salmon sperm DNA). Final washes were at 55 to 60°C in .7x SSC, 5% SDS for 15 to 20 min.