Abstract
Native calf thymus and salmon sperm DNA are better templates than denatured calf thymus and salmon sperm DNA for the DNA‐dependent DNA polymerase activity of feline sarcoma virus. This enzyme activity of feline sarcoma virus and feline leukemia virus faithfully replicates dAT copolymer to synthesize a sequence of alternate deoxyadenylate‐deoxythymidylate. With a homopolymeric duplex, polydA.dT, the DNA‐directed enzyme from feline sarcoma virus or feline leukemia virus indicates a requirement for simultaneous copying of both template strands.