LIFE SCIENCE

Detailed explanation-1: -Bacteria protect themselves from viruses by fragmenting viral DNA with an endonuclease. The endonuclease is also known as restriction enzyme which is a protein that is produced by bacterial cells which leaves DNA at specific sites along with the molecule.

Detailed explanation-2: -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-3: -If the virus comes back, the bacterium makes RNA from the region of CRISPR specific for that virus. These RNA copies pair up with some cas (CRISPR-associated) proteins. The RNA guides the cas protein to the invading viral DNA, so the protein can destroy it.