Question

Match the following enzymes of DNA replication with their respective functions:
$\begin{array}{cc}\text{Column I}& \text{Column II}\\ \text{p. DNA polymerase}& \text{i. Helps unzip the DNA double helix}\\ \text{q. DNA ligase}& \text{ii. Seals nicks between Okazaki fragments}\\ \text{r. DNA helicase}& \text{iii. Lays RNA primers to which polymerase can add nucleotides}\\ \text{s. Primase}& \text{iv. Adds nucleotides to the free 3' end of RNA primers}\end{array}$

• 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

DNA replication is the process by which two identical copies of DNA are created from one DNA molecule.

A lot of enzymes are involved in this process.

DNA helicase is involved in unzipping the DNA double helix, which it achieves by breaking up the hydrogen bonds between the nucleotides of each base pair.

Primase 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.

Hence, 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.