Which of the following enzyme(s) are NOT essential for gene cloning?
A.   Restriction enzymes

B.    DNA ligase

C.    DNA mutase
D.     DNA recombinase
E.      DNA polymerase
Choose the correct answer from the options given below:

Gene cloning generally involves three key steps: cutting the donor DNA, inserting it into a vector, and sealing the recombinant DNA so it can be propagated in a host. The enzymes that directly perform these indispensable steps are:

Restriction enzymes – they cleave DNA at specific sequences, creating compatible ends for insertion.
DNA ligase – it joins the DNA fragments, sealing the phosphodiester backbone of the recombinant molecule.
DNA polymerase – while not always required for the ligation step itself, it is necessary for the replication of the plasmid inside the host cell, ensuring that the cloned gene is maintained and amplified.

In contrast, the following enzymes are not required for the basic cloning workflow:

DNA mutase (option C) – this enzyme introduces specific base changes in DNA, which is useful for site‑directed mutagenesis but is not needed to simply clone a gene.
DNA recombinase (option D) – recombinases mediate site‑specific recombination events, a technique employed in advanced cloning strategies (e.g., Cre‑Lox), yet they are not essential for standard restriction‑enzyme‑based cloning.

Since only the enzymes listed in options C and D are non‑essential, the correct selection is **C and D only**.