The XPD helicase family comprises XPD and several related super-family 2 DNA helicases including DDX11/ChlR1 (DEAD/DEAH box helicase 11), RTEL1 (regulator of telomere elongation 1), and FANCJ (Fanconi anemia complementation group J). This evidence concerns the gene RTEL1 and Fanconi anemia.