question: What is the main biological function of the CRISPR-CAS9 genome editing system?
answer: The CRISPR/Cas9 system (clustered regularly interspaced short palindromic repeats/CRISPR-associated) has recently emerged as an efficient and simple tool for site-specific engineering of eukaryotic genomes. The CRISPR/Cas9 system has attracted significant attention for its potential to transform genome engineering. It has been shown that the RNA-guided Cas9 nuclease can be employed to engineer the Drosophila genome, and that these modifications are efficiently transmitted through the germline. The CRISPR/Cas9 system has been reported to efficiently induce targeted gene disruption and homologous recombination in both prokaryotic and eukaryotic cells. The CRISPR/Cas9 system has been used to create knock-out alleles with great efficiency, and it has also been employed in knock-in of DNA cassettes at defined loci via homologous recombination (HR). The ease and efficiency of the CRISPR/Cas9 system with limited off-target effects make it a powerful genome engineering tool for in vivo studies.