RNases, or ribonucleases, are a broad class of RNA-degrading enzyme possessed by all organisms, and are extremely common in the environment. Because RNase is specific to cleaving RNA molecules, the enzyme is commonly used in molecular biology for removal of RNA within DNA and protein samples. In nuclease protection assays, individual RNA segments can be probed and hybridized, while unhybridized RNA are degraded by added RNase. Common RNase subclasses used in molecular biology are RNase A and RNase H.