Question

What is responsible for filling the gap left by the nucleases that digest the primer and the short DNA segment added to it by polymerase α?

a. DNA polymerase β
b. DNA polymerase δ
c. DNA polymerase ε
e. RNase H1

Answer 1

DNA polymerase I is responsible for replacing the RNA primer with DNA nucleotides during DNA replication. It also removes the primer with its exonuclease activity, and DNA ligase seals the resultant DNA segments.

Step-by-step explanation:

The enzyme responsible for filling the gap left by the nucleases that digest the RNA primer and the short DNA segment added to it by polymerase α (alpha) is DNA polymerase I. This enzyme not only has the ability to add DNA nucleotides in place of the RNA primer but also possesses a 5'→3' exonuclease activity that is responsible for removing RNA primers at the terminal end. Once DNA polymerase I has replaced the RNA with DNA, DNA ligase is responsible for sealing the ends of the new segments, particularly the Okazaki fragments, ensuring continuity of the DNA strand.