Question

• what role does cas9 play in the crispr system
• enzyme that can cut target dna and disable virus -

Explanation:

The question is about the role of Cas9 in the CRISPR system. In the CRISPR - Cas9 system, Cas9 is a type of enzyme (specifically an endonuclease). Its main role is to act as a molecular scissors. It can recognize and bind to the target DNA sequence that is complementary to the guide RNA (in the CRISPR system). Then, it makes a double - stranded break in the target DNA. This function is crucial for processes like gene editing, where we can introduce changes to the DNA sequence. Also, in the context of the immune system of bacteria (from which the CRISPR - Cas9 system is derived), Cas9 can cut the DNA of invading viruses, thereby helping the bacteria to defend against viral infections.

Answer:

Cas9 is an enzyme (endonuclease) in the CRISPR system. It can recognize the target DNA sequence (with the help of guide RNA), cut the target DNA (make double - stranded breaks), and in bacterial immunity, it can cut the DNA of invading viruses to help bacteria defend against viral infections. In gene - editing applications, this DNA - cutting ability is used to introduce changes to the DNA sequence.