A, The intron-exon boundaries of RECQL4 gene. Exon 7 is deleted by the RAPA patient mutation, black filled rectangles. Exons 8–14, hatched, encode the RecQ helicase domain. B, Simply Blue stained SDS-PAGE gel of bacterially expressed and purified WT and RAPA RECQL4 proteins, 500 ng of each full length protein. C, Denaturation curves for 2× Sypro Orange control, dashed line, and WT RECQL4 plus 2× Sypro Orange, solid line. Insert shows original raw fluorescence values versus temperature, which the denaturation curve is extrapolated from.