TP53 and Infertility: Figure 4B shows that wild-type females recovered from infertility within 1 week post-exposure to IR at a dose of 11.5 krad. In contrast, females lacking p53 remained permanently infertile even when tracked over 2 weeks after IR (Figure 4B). To confirm that p53 gene function is responsible for this phenotype, we tested p53− females carrying a genomic rescue fragment spanning the p53 gene (see ‘Materials and methods’). We tested two rescue strains and in both cases the sterility defect was reversed (Figure 4B).