What is the endogenous purpose of CRISPR?
For multi-celled organisms, genomic alterations are usually a minor inconvenience – the offending cell is removed and replaced. However, single-celled organisms obviously cannot do this, and genomic alterations can result in organism death or dramatic functional alterations and an inability to thrive. The CRISPR/Cas system is particularly designed to ward off viruses, which attempt to hijack endogenous DNA transcription mechanisms for their own purposes.
1. D. Rath, et al., “The CRISPR-Cas immune system: biology, mechanisms and applications,” Biochimie 117:119-128, 2015.
2. K.S Makarova, et al., “Evolution and classification of the CRISPR-Cas systems,” Nat Rev Microbiol 9(6): 467-477, 2011.