Which enzyme is responsible for removing RNA-DNA hybrids during lagging strand synthesis?

The enzyme responsible for removing RNA-DNA hybrids during lagging strand synthesis is RNase H. During DNA replication, especially on the lagging strand, RNA primers are synthesized to initiate the formation of Okazaki fragments. These RNA primers are essential for starting DNA synthesis because DNA polymerases require a free 3'-OH group to add nucleotides.

Once the DNA synthesis catches up to the RNA primer section, the RNA must be removed to allow for a seamless DNA strand. RNase H specifically recognizes and degrades the RNA strand of RNA-DNA hybrids, facilitating the removal of these RNA primers. After RNase H acts on the hybrid, another enzyme, typically DNA polymerase, fills in the gaps by synthesizing DNA complementary to the remaining DNA template. This process ensures that the final DNA product is entirely composed of DNA, which is crucial for genomic integrity and function.

The other enzymes mentioned have distinct roles in the replication process. Helicase unwinds the DNA double helix, DNA ligase joins the Okazaki fragments by sealing nicks in the sugar-phosphate backbone, and primase synthesizes the RNA primers necessary for initiating synthesis. None of these processes directly involve the removal of RNA-DNA hybrids during lagging strand synthesis,