Restriction enzymes belong to a larger class of enzymes called nucleases. These are of two kinds; exonucleases and endonucleases. Exonucleases remove nucleotides from the ends of the DNA whereas, endonucleases make cuts at specific positions within the DNA. Each restriction endonuclease functions by ‘inspecting’ the length of a DNA sequence. Once it finds its specific recognition sequence, it will bind to the DNA and cut each of the two strands of the double helix at specific points in their sugar-phosphate backbones. Each restriction endonuclease recognises a specific nucleotide sequences in the DNA.
Nucleases represent what type of enzyme
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → Hydrolases
Nucleases break the phosphodiester bonds of nucleic acids by adding water: they are hydrolases. Restriction enzymes are only one group of nucleases.
Option (1) Peptidases — Incorrect. Peptidases break the peptide bonds of proteins. Nucleases act on nucleic acids such as DNA, so they are not peptidases.
Option (2) Lipases — Incorrect. Lipases break down fats; NCERT mentions them in detergents for removing oily stains. They do not act on DNA.
Option (3) Restriction enzymes — Incorrect. Restriction enzymes are a part of the nucleases, not the class they belong to.
Option (4) Hydrolases — Correct. Nucleases break the phosphodiester bonds of nucleic acids by adding water across them, so they are hydrolases (hydrolysing enzymes).
Note: The passage is taken from NCERT. NTA has put lines of the NCERT text together to make it. Most CUET (UG) questions come straight from NCERT, so study the book line by line, including figures and their titles.