Final answer:
The statement regarding the restriction-modification system involving two genes, the cutting enzyme (restriction endonuclease) and the methylating enzyme (DNA methylase), is true. These components work together to protect bacterial DNA and cleave foreign DNA.
Step-by-step explanation:
The statement that the restriction-modification system always involves two genes, the cutting enzyme and the methylating enzyme, is true. In bacteria, the restriction-modification system is crucial for distinguishing self from non-self DNA, typically that of invading viruses. The system includes two main components: (a) DNA methylase (the methylating enzyme) that adds methyl groups to specific DNA sequences, thereby protecting the host DNA from being cut, and (b) restriction endonucleases (the cutting enzymes) that cleave non-methylated DNA at the same specific sequences.DNA methylation serves as a protective marker for the host DNA. This ensures that the cell's own DNA is not attacked by its own restriction endonucleases, whereas foreign DNA lacking these methyl groups is recognized as an invader and subsequently cleaved, hence referred to as "restricted DNA". This system plays an important role in bacterial immunity against bacteriophages and other potentially harmful genetic elements.