To create bmx mice (for Becker muscular dystrophy, X‐linked) that model the most common BMD patient mutation,14 we used CRISPR/Cas9 to introduce a ~40 000 bp genomic deletion into the endogenous murine dystrophin (Dmd) gene, excising exons 45–47. The gene discussed is DMD; the disease is Becker muscular dystrophy.