What is CRISPR?

• A. Sequences of bacterial DNA derived from viral DNA fragments.
• B. A gene editing tool.
• C. A bacterial defense mechanism against viral infections.
• D. All of the above.

Answer: (D)

Verified step by step guidance

1. Understand that CRISPR stands for 'Clustered Regularly Interspaced Short Palindromic Repeats,' which are sequences of DNA found in bacteria and archaea.
2. Recognize that these DNA sequences are derived from fragments of viral DNA that have previously infected the bacteria, allowing the bacteria to 'remember' the virus.
3. Learn that CRISPR functions as a bacterial defense mechanism by using these sequences to recognize and cut viral DNA during subsequent infections, effectively neutralizing the virus.
4. Understand that scientists have adapted the CRISPR system, particularly the Cas9 protein, as a powerful gene-editing tool to target and modify specific DNA sequences in various organisms.
5. Conclude that CRISPR is all of the above: a sequence of bacterial DNA derived from viral DNA, a bacterial defense mechanism, and a gene-editing tool.