Question

Genetic engineering is possible, because

• A. The phenomenon of transduction in bacteria is well understood
• B. We can see DNA by electron microscope
• C. We can cut DNA at specific sites by endonucleases such as DNAase I
• D. Restriction endonucleases purified from bacteria can be used in vitro

Answer 1

Answer: (D)

A restriction enzyme or restriction endonuclease is an enzyme that cuts DNA at or near specific recognition nucleotide sequences known as restriction sites. These enzymes are found in bacteria and archaea and provide a defense mechanism against invading viruses. Inside a prokaryote, the restriction enzymes selectively cut up foreign DNA in a process called restriction; while host DNA is protected by a modification enzyme (a methyltransferase) that modifies the prokaryotic DNA and blocks cleavage. Together, these two processes form the restriction-modification system. These enzymes are routinely used for DNA modification in laboratories and are a vital tool in molecular cloning.

Therefore, the correct answer is option D.