In molecular genetics, during DNA replication, the Okazaki fragments on the lagging strand are covalently joined together by the enzyme:
Answer and explanation
Correct answer: A. DNA ligase
- Step 1: During replication of the lagging strand, DNA polymerase synthesizes discontinuous Okazaki fragments in the direction away from the replication fork, each preceded by an RNA primer.
- Step 2: After DNA polymerase I removes the RNA primers and fills the gaps with deoxyribonucleotides, DNA ligase catalyzes the final formation of covalent phosphodiester bonds between adjacent 3'-hydroxyl and 5'-phosphate ends to seal the backbone.
Answer
DNA ligase.
Why not the others: DNA polymerase III synthesizes the leading strand and elongates Okazaki fragments but cannot seal nicks between adjacent fragments; Helicase unwinds the double helix at the replication fork; RNA primase synthesizes short RNA primers required to initiate DNA synthesis.
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