Question

Match the following enzymes of DNA replication with their respective functions:

p. DNA polymerase i. Helps unzip the DNA double helix

q. DNA ligase ii. Seals nicks between Okazaki fragments

r. DNA helicase iii. Lays RNA primers to which polymerase can add nucleotides

s. Primase iv. Adds nucleotides to the free 3’ end of RNA primers

• A. p-i, q-ii, r-iii, s-iv
• B. p-iii, q-i, r-ii, s-iv
• C. p-iv, q-ii, r-i, s-iii
• D. p-ii, q-iii, r-iv, s-i

Answer 1

The correct option is C

p-iv, q-ii, r-i, s-iii

Among the major enzymes involved in DNA replication, DNA polymerase primarily performs the task of adding nucleotides to the free 3’ end of the RNA primers. DNA ligase seals up any nicks formed in the newly synthesized DNA strands, such as those between Okazaki fragments in the lagging strand and between the fragment that replaced primer and the rest of the nucleotides added by DNA polymerase. However, ligase does not add nucleotides (which is done only by polymerase) to fill in gaps. DNA helicase is involved in unzipping the DNA double helix, which it achieves by breaking up of the hydrogen bonds between the nucleotides of each base pair. Primase, specifically the RNA primase enzyme, lays down the short RNA primers at the beginning of replication so that, DNA polymerase can start adding nucleotides to the free 3’ end of the primers to form the new strands.