Ribonuclease H (RNase H) <db_xref db="EC" dbkey="3.1.26.4"/> recognises and cleaves the RNA strand of RNA-DNA heteroduplexes. In prokaryotes RNase H is involved in removing the RNA of RNA-DNA hybrids, particularly the primers of Okazaki fragments in lagging-strand DNA synthesis [<cite idref="PUB00018345"/>].