The linking of antibiotic resistance gene with the plasmid vector became possible with:
- Exonucleases
- Endonucleases
- DNA ligase
- DNA polymerase
Answer
(3) DNA ligase
Solution
Restriction endonucleases only cut DNA at specific recognition sequences, producing sticky ends, and exonucleases remove nucleotides from the ends.
The cut antibiotic resistance gene and the cut plasmid vector still have to be joined by forming phosphodiester bonds between their sugar–phosphate backbones.
As per NCERT, the enzyme DNA ligase joins the DNA fragments, so the linking of an antibiotic resistance gene with a plasmid vector (the first recombinant DNA, made by Cohen and Boyer in 1972) became possible with DNA ligase.
Answer: (3)