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. Author manuscript; available in PMC: 2021 Oct 1.
Published in final edited form as: Nat Protoc. 2021 Mar 10;16(4):2088–2108. doi: 10.1038/s41596-020-00485-y

Figure 2.

Figure 2.

Principles of the homing CRISPR system. (a) Canonical CRISPR sgRNAs and Cas9 protein target the locus containing a spacer and PAM leading to mutations in the target locus. (b) Homing CRISPR system barcoding element. The hgRNA transcript expressed by the locus forms a complex with Cas9 protein and targets the locus for double-strand break. As the NHEJ repair system repairs the cut, it introduces mutations in the hgRNA locus. These random mutations can effectively act as barcodes. (c) sgRNAs (left) are limited to a single round of targeting and mutagenesis. hgRNAs (right) can undergo multiple rounds of targeting and mutagenesis, expanding their allelic diversity. Panel b is adapted with permission from ref. 7.