Preparation of dsDNA and dsRNA substrates for 59 phosphatase activity dsDNA was made by annealing of sense and antisense primers (D159A). Resulting annealed product was end labelled using [c-32 P] ATP as described above. Further, dsDNA was gel eluted from the mixture of dsDNA and ssDNA. dsRNA was generated by annealing of in vitro transcribed sense and antisense 1 kb Sesbania mosaic virus RNA transcripts (kind gift from K. Govind). dsRNA was separated from ssRNA on 1% Agarose gel and dsRNA was gel eluted. The concentration of dsDNA/dsRNA was determined by measuring the O.D. at 260 nm in a spectrophotometer.