Abstract
CRISPR/Cas9 systems have revolutionised the field of gene editing, allowing for precise modifications to be generated in vivo to mimic the genetic events found in human cancer cells. These systems may be used to generate germline or somatic loss-of-function of events, and also chromosomal rearrangements, either constitutively or in a spatiotemporally controlled manner. Forward genetic screens have also been performed using CRISPR/Cas9 systems to identify new driver genes and approaches using catalytically inactive Cas9 fused to base editors have enabled genome editing with single-base precision. Here we discuss the many 'flavours' of the CRISPR/Cas9 system and give examples of their use for the generation of clinically-relevant mouse models of cancer.