Given that RECQL5 gene amplification and deficiency have both been associated with cancer predisposition, it is possible that RECQL5 is required at a suitable level to permit sufficient RAD51-mediated strand invasion for HR repair without an excess of D-loop formation biasing outcomes toward dHJ and CO products (Olson et al., 2018; Wright et al., 2018; Zhu et al., 2018). This evidence concerns the gene RECQL5 and cancer.