Question

Which enzyme is used to join two DNA fragments in genetic engineering?

• A. Restriction endonuclease
• B. DNA polymerase
• C. RNA polymerase
• D. DNA ligase

Hint:

Think of genetic engineering as a two-step process: cutting DNA at target sites, then sealing the cut ends back together into one molecule. Recall which class of enzyme handles the sealing step, specifically the one that closes a nick in the DNA backbone by forming a new bond.

Answer 1

The Correct Option is D

The correct answer to the question "Which enzyme is used to join two DNA fragments in genetic engineering?" is DNA ligase.

Here is a detailed explanation:

1. DNA Ligase:
   • DNA ligase is an enzyme that facilitates the joining of DNA strands together by catalyzing the formation of a phosphodiester bond.
   • This enzyme is crucial in genetic engineering and molecular cloning because it joins DNA fragments together, such as inserting a DNA fragment into a plasmid vector.
2. Explanation of Other Options:
   • Restriction Endonuclease: These enzymes cut DNA at specific sequences and are used to create fragments with sticky ends that can be recombined, but they do not join fragments.
   • DNA Polymerase: This enzyme is involved in DNA replication and synthesizes new DNA strands from a template. It does not join DNA fragments.
   • RNA Polymerase: This enzyme synthesizes RNA from a DNA template during transcription and is not involved in joining DNA fragments.

In conclusion, DNA ligase is the enzyme specifically used to join two DNA fragments in genetic engineering, making it essential for the process of DNA recombination.