Bacteria protect themselves from phages by producing the following enzymes which fragment the phage genome
Bacteria protect themselves from phages by producing the following enzymes which fragment the phage genome
Select an option to attempt
Correct Answer: Option B
Explanation
Bacteria use the restriction-modification (R-M) system to defend against bacteriophage DNA. Restriction endonucleases recognise specific short palindromic sequences in foreign DNA and cleave both strands. The bacterium's own DNA at the same recognition sites is protected by methylation (by cognate methyltransferases) — methylated bases are not cut by the cognate restriction enzyme. This creates a molecular immune system that distinguishes 'self' from 'non-self' DNA. Common restriction enzymes (EcoRI, BamHI, HindIII) are derived from bacterial R-M systems and are essential tools in molecular biology.