Transgene-free genome editing by germline injection of CRISPR/Cas RNA

Genome modification by CRISPR/Cas offers its users the ability to target endogenous sites in the genome for cleavage and for engineering precise genomic changes using template-directed repair, all with unprecedented ease and flexibility of targeting. As such, CRISPR/Cas is just part of a set of recently developed and rapidly improving tools that offer great potential for researchers to functionally access the genomes of organisms that have not previously been extensively used in a laboratory setting. We describe in detail protocols for using CRISPR/Cas to target genes of experimental organisms, in a manner that does not require transformation to obtain transgenic lines and that should be readily applicable to a wide range of previously little-studied species.