HOXA9 targeting and genotypic analysis. (A) Normal HOXA9 genomic locus is shown on top and the targeted locus on the bottom. Arrowheads marked a-9#1, a-9#2, and neo denote primer sites for genotyping by PCR. (B) PCR products from tail or toe DNA, amplified using the 3 primers shown in (A). Amplification of the wild-type allele with primers a-9#1 and a-9#2 results in the lower 123-nt band, whereas amplification of the targeted allele with primers a-9#1 and neo results in the upper 200-nt band (arrows). The gel shows results from normal (lanes 1, 2, 3, and 8), HOXA9+/− (lane 4), and HOXA9−/− (lanes 5 and 6) animals. Lane 7 is a control (C) lane with no DNA.