Fig. 5. Myoglobin gene disruption strategy. (A) The myoglobin (Mb) gene consists of three exons. To produce knockout mice that lack myoglobin, exon 2 was replaced with a neomycin cassette (neo), and homologous recombination technology was used as previously described (Garry et al., 1998). (B) Compared with the wild-type adult soleus muscle (above), which is an oxidative muscle group, the myoglobin-deficient soleus muscle (below) was depigmented.