[Synthesis of double-stranded DNA on light immunoglobulin chain matrix RNA]

cDNA was synthesized on Ig kappa-L-chain mRNA isolated from mouse plasmocytoma MOPC 21 using avial myeloblastosis RNA-dependent DNA polymerase. The cDNA was used as a matrix for second DNA chain synthesis using 5'-exonuclease free DNA-polymerase I (Klenoff fragment). Hairpin DNA having double length of initial cDNA was obtained without added exogenous primer. SI nuclease treatment of the hairpin DNA results in reducing the DNA length twice, as shown by electrophoresis in denaturing conditions. The fact, that S1 nuclease resistance of the hairpin DNA is 75% shows high complementarity between first and second DNA chain. The product length obtained after S1 nuclease treatment was shown to be heterogenous. The maximal length of the product, reaching at least 900 base pairs, is near to be initial mRNA length (without the poly(A)-fragment).