Synthesis of DNA complementary to the mRNAs for milk proteins by E. coli DNA polymerase I

E.Coli DNA polymerase I (Klenow subfragment) was used for the synthesis of complementary DNA with the mRNAs for rabbit milk proteins as templates. The cDNA formed, contained 200 nucleotides and represented about 20% of the mRNA template. The cDNA was hybridized specifically to the mRNA templates. The Klenow subfragment of the E.Coli DNA polymerase I was as efficient as the avian myeloblastosis virus reverse transcriptase in the synthesis of cDNA. The mean size of the cDNA fragments obtained with the Klenow enzyme proved to be 70% of the value obtained with the AMV reverse transcriptase and at least twice the value generally obtained with the complete E.Coli DNA polymerase I. The cDNA was used for the detection and the quantification of the mRNA template in various RNA fractions.