NZY RNase H is a recombinant endoribonuclease purified from an Escherichia coli strain that over-expresses the cloned RNase H gene (rnh). The enzyme specifically hydrolyses the phosphodiester bonds of RNA which is hybridized to DNA to produce 5´ phosphate-terminated oligoribonucleotides and single-stranded DNA. RNase H does not degrade single and double-stranded DNA or unhybridized RNA. It is a key enzyme in the removal of mRNA after first-strand cDNA synthesis. Treating cDNA with RNase H prior to PCR can improve sensitivity as cDNA-RNA hybrids in the amplification reaction may prevent binding of the amplification primers. RNase H treatment is often necessary when amplifying longer, full-length cDNA targets.