Box 1.

Generation of point mutations using CRISPR/Cas9 based Genome editing

Targeted editing in flies, especially at the level of changing a single amino-acid has been a challenging task. In the past, point mutations were routinely generated by large chemical mutagenesis screens at random sites and mutations of interest subsequently identified, enriched and stabilized 165,166. The second routine method to study mutants was to first generate null flies for the target locus and rescue the null by expression of either wild-type or mutant allele, usually by inserting the transgene at a site distant from the target locus 167,168. In recent years, the utility of the CRISPR/Cas9 toolbox to edit the genomic locus directly and efficiently has revolutionized fly biology. After the initial demonstration of CRISPR/Cas9 genome editing in mammalian cells 169–173, fly biologists developed equivalent methodologies to engineer the fly 158,159,174. Today, a fly biologist can routinely generate site directed mutations, such as replacing a target lysine with an arginine, creating a SUMO resistant site, using the CRISPR/Cas9 toolbox in the fly.