Question

Enzymes that remove nucleotides one at a time from the end of a DNA molecule are called

• A. Ligases
• B. Exonucleases
• C. Endonucleases
• D. DNases

Hint:

Exonucleases are important for DNA repair and are used in processes such as DNA sequencing and genetic engineering.

Answer 1

The Correct Option is B

Exonucleases are enzymes that remove nucleotides from the ends of DNA molecules. They act by cleaving one nucleotide at a time from either the 3' or 5' end of the DNA strand.

(1) Exonucleases:
- These enzymes are responsible for the degradation of DNA by removing nucleotides one by one from the ends of the DNA molecule, either from the 3' or 5' end.

(2) Why Other Options Are Incorrect:
- Ligases (Option 1) are enzymes that catalyze the formation of phosphodiester bonds between adjacent nucleotides, joining DNA fragments rather than removing nucleotides.
- Endonucleases (Option 3) are enzymes that cleave the phosphodiester bond within the DNA strand, not at the ends.
- DNases (Option 4) are a broader class of enzymes that degrade DNA, but exonucleases specifically refer to those that remove nucleotides from the ends of the DNA.

Conclusion: The enzymes that remove nucleotides one at a time from the end of a DNA molecule are called exonucleases.