M.Prasad Naidu discusses several types of polymerases including DNA-dependent DNA polymerases, DNA-dependent RNA polymerases, RNA-dependent DNA polymerases, and RNA-dependent RNA polymerases. Reich et al. and Baltimore and Franklin demonstrated RNA-primed RNA synthesis using the enzyme RNA-dependent RNA polymerase, also called RNA replicase. Spiegelman et al. isolated RNA replicase from bacteriophage Qβ which requires an RNA template, magnesium ions, and ribonucleoside triphosphates to function.