Fig. 1

Biology of natural CRISPR-Cas9 system of Streptococcus pyogenes and its synthetic counterpart. As the bacteriophage infects a bacterial cell, pieces of phage derived DNA (known as spacers) are inserted in the CRISPR array within CRISPR Cas locus. Following the event of reinfection, the CRISPR array is transcribed. A trans-activating CRISPR RNA (tracrRNA) is also transcribed. CRISPR RNA (crRNA):tracrRNA complexes are derived by the activity of RNase III. The spacer sequence is targeted by the crRNA:tracrRNA:Cas9 complex and cleaved. In case of synthetic systems, cleavage of target sequence is achieved by the activity of single guide RNA (sgRNA)-Cas9 complex. Double strand break is repaired either by the non-homologous end joining (NHEJ) or homology directed repair (HDR) mechanism. Created with BioRender.com with granted permission and license