Final answer:
Bacteria use the CRISPR/Cas9 system as an immune strategy by inserting excised phage DNA into their genome; upon re-infection, RNA markers guide Cas9 to the viral DNA for destruction. The system is also utilized in genetic engineering to edit genes. Bacteria do not duplicate the viral DNA but create RNA markers for Cas-based targeting.
Step-by-step explanation:
Understanding Bacterial Immunity Through the CRISPR/Cas9 System
In bacterial immunity, the CRISPR/Cas9 system plays a pivotal role. When a bacterium encounters a virus (phage), it uses the Cas9 protein as part of an adaptive immune strategy. Initially, when the phage DNA is detected, it is excised and inserted into the CRISPR region of the bacterial genome. The sequence acts as a record of the viral infection. Upon subsequent exposure to the same phage, the bacterium produces RNA markers from this recorded DNA segment, which guide the Cas9 protein to the viral DNA, allowing it to cleave and thus neutralize the threat.
The CRISPR system is also at the forefront of genetic engineering technology. Researchers have tapped into this mechanism to edit genes within organisms, including the possibility of fixing genes responsible for heritable diseases. This innovation has made genomic modifications more accessible for molecular biology labs around the world.
It is important to clarify that bacteria do not duplicate the copied virus DNA once it is inserted into their genome. Instead, they transcribe it into RNA, which then guides the Cas proteins to target and destroy the viral DNA upon re-infection. This process is a key component of bacterial defense systems and is transmitted to progeny cells, ensuring continuity of immunity against specific phage attacks.