BIOMOLECULES AND ENZYMES

Detailed explanation-1: -A bacterium uses a restriction enzyme to defend against bacterial viruses called bacteriophages, or phages. When a phage infects a bacterium, it inserts its DNA into the bacterial cell so that it might be replicated. The restriction enzyme prevents replication of the phage DNA by cutting it into many pieces.

Detailed explanation-2: -Bacteria protect their DNA by modifying their own recognition sequences, usually by adding methyl (CH3) molecules to nucleotides in the recognition sequences and then relying on the restriction enzymes’ capacity to recognize and cleave only unmethylated recognition sequences.

Detailed explanation-3: -Definition. A restriction enzyme is a protein isolated from bacteria that cleaves DNA sequences at sequence-specific sites, producing DNA fragments with a known sequence at each end. The use of restriction enzymes is critical to certain laboratory methods, including recombinant DNA technology and genetic engineering.

Detailed explanation-4: -The bacterial cell uses the restriction enzyme to cut the invading DNA of the virus at the specific recognition site of the enzyme. This prevents the virus from taking over the cellular metabolism for its own replication.

Detailed explanation-5: -These enzymes occur naturally in bacteria as a defense against bacteriophages – viruses that infect bacteria. Bacterial restriction enzymes cut the invading bacteriophage DNA while leaving the bacterial genomic DNA unharmed due to addition of methyl groups.