Fig. 2.

Historical timeline of discoveries of the components of the CRISPR–Cas9 system. 1987 – Short DNA repeats, later called CRISPR, were first noticed in bacterial genomes, and, in 1995, also found in archaea. 2005 – The role of CRISPR loci in the protection of prokaryotes from foreign genetic information was proposed, and the Cas9 protein was described for the first time (initial information on proteins associated with the CRISPR locus appeared in 2002). Two RNA molecules, crRNA and tracrRNA, were discovered as part of the complex in 2007 and 2011, respectively. The Nobel Prize-winning work, where all of the components were assembled in vitro and two RNA molecules combined into one strand for the ease of use of the system, was published in 2012.