Read the following passage carefully.

Restriction enzyme

Restriction enzymes cut the strand of DNA a little away from the center of the palindrome sites, but between the same two bases on the opposite strands. This leaves single stranded portions at the ends. There are overhanging stretches called sticky ends on each strand. These are named so because they form hydrogen bonds with their complementary cut counterparts. This stickiness of the ends facilitates the action of the enzyme DNA ligase. The word palindromes refer to group of letters that forms the same words when read both forward and backward. Restriction endonucleases are used in genetic engineering as molecular scissors.

Which one of the following enzyme helps to join DNA?

DNA ligase

The correct answer is Option (3) → DNA ligase   

DNA 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.

Endonuclease → Cuts DNA/RNA at specific internal sites.

Polymerase → Synthesizes new DNA or RNA strands.