PRKDC and myeloid leukemia: To test how mutations in the DNA repair genes affect the relative amount of HDR in a different cell type and when using CRISPR enzymes that produce different types of DNA breaks, we introduced the DNA-PKcs K3753R, Polθ V896* and RAD52 K/R152–156A mutations singly and in three combinations (no clones could be obtained for the triple mutant combination) in a human myelogenous leukemia line (K562) using the ribonucleoprotein (RNP) high fidelity Cas9 variant (Cas9-HiFi)33.