At this stage, Blm−/− mutant embryos are greatly underrepresented from the expected Mendelian ratio (five-fold) (Fig. 4a and Supplementary Fig. 9g), and those few that are obtained are dead, exhibiting developmental delay and severe anemia (Fig. 4b and Supplementary Fig. 10a), as reported. The gene discussed is BLM; the disease is anemia (phenotype).