Assertion: Genetic engineering requires both nucleases and ligases.
Reason: Ligases produce the nick in the recombinant DNA molecule.
Answer & explanation
Correct answer: option 3
Nucleases are the enzymes that remove nucleotides or produce nick in the DNA strand. Exonucleases remove nucleotides from the free ends of DNA while endonucleases produce internal nick in DNA. Now, the desired gene is inserted and the cut ends are sealed with the help of DNA ligase. Ligases are also called molecular glue as they join together two strands by forming phosphodiester bonds between adjacent nucleotides.