Which of the following enzymes join the sticky ends in recombinant DNA technology?

Ligase

The correct answer is Option (3) → Ligase   

Ligase → Joins (seals) two fragments of DNA together by forming a phosphodiester bond. That’s why it is called the “molecular glue” in genetic engineering. For example, DNA ligase is used in recombinant DNA technology to join foreign DNA with a plasmid.

Exonuclease → Cuts nucleotides one by one from the end of DNA/RNA.

Endonuclease → Cuts DNA/RNA at specific internal sites.

Chitinase → Chitinase is an enzyme that breaks down chitin, a structural polysaccharide found in the cell walls of fungi and some bacteria.