Question

Bacteria protect themselves from viruses by fragmenting viral DNA upon entry with _____________.

• A. Methylase
• B. Endonucleases
• C. Ligases
• D. Exonucleases

Answer 1

The correct option is B Endonucleases

Restriction enzyme, also called restriction endonuclease, a protein produced by bacteria that cleaves DNA at specific sites along the molecule. In the bacterial cell, restriction enzymes cleave foreign DNA, thus eliminating infecting organisms. 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. Restriction enzymes were named for their ability to restrict, or limit, the number of strains of bacteriophage that can infect a bacterium.

So, the correct answer is 'Endonucleases'