Which one of the following enzymes acts as molecular scissors?

The correct answer is Option (3) → Restriction enzymes

Option (1) DNA polymerase — Incorrect. DNA polymerase builds a new DNA strand by joining nucleotides on a template during replication. It joins; it does not cut.

Option (2) RNA polymerase — Incorrect. RNA polymerase copies a gene into RNA during transcription. It does not cut DNA either.

Option (3) Restriction enzymes — Correct. A restriction enzyme recognises a specific base sequence (a palindrome) in DNA and cuts the DNA at that place, as EcoRI does. Like a pair of scissors, it cuts at a chosen point, which lets a gene be cut out and joined to a vector.

Option (4) Helicase — Incorrect. Helicase unwinds the two strands of the DNA double helix during replication by breaking the hydrogen bonds between the bases. It separates the strands but does not cut the DNA into pieces.

Note: A similar question was also asked in CUET (UG) 2026 on 26-05-2026 (Slot 1), and in CUET (UG) 2023 on 11-06-2023 (Slot 3).

NCERT Extract:
Principles of Biotechnology – “… The construction of the first recombinant DNA emerged from the possibility of linking a gene encoding antibiotic resistance with a native plasmid (autonomously replicating circular extra-chromosomal DNA) of Salmonella typhimurium. Stanley Cohen and Herbert Boyer accomplished this in 1972 by isolating the antibiotic resistance gene by cutting out a piece of DNA from a plasmid which was responsible for conferring antibiotic resistance. The cutting of DNA at specific locations became possible with the discovery of the so-called ‘molecular scissors’– restriction enzymes. The cut piece of DNA was then linked with the plasmid DNA.”