Biotechnology: Principles and Processes — BIOLOGY STD 12 Science — Question

3. Both A and B

Explanation:

Restriction systems identify the origin of incoming DNA and destroy it 

if recognized as foreign. Restriction endonucleases recognize specific 

sequences in the incoming DNA and digest the DNA into fragments. They 

cut the DNA either at specific sites or more randomly. Hence, 

restriction endonucleases are synthesized by bacteria as part of their defense mechanism. These enzymes are used in genetic engineering to cut the gene of the interest from source DNA and to introduce them into the vectors; but this is not a natural function of restriction endonucleases. Transcription is the process of synthesis of RNA using the DNA template. RNA polymerase perform this function by adding ribonucleotides to the RNA primer. Translation of nucleotide sequence of mRNA into amino acid sequence of protein is called as protein synthesis. It is performed by tRNA. Restriction enzymes do not play any role in these two processes.