L-gulonolactone oxidase (GULO), the final enzyme in the biosynthetic pathway of ascorbic acid (vitamin C), is a subject that comes up often in discussions of common ancestry. The functioning GULO gene allows most plants and many animals to produce vitamin C from glucose or galactose. In some taxa, however, the GULO gene does not function in this capacity and is given the “pseudogene” label. The GULO gene is thought to be broken in humans (Nishikimi and Yagi, 1991), primates and guinea pigs (Nishikimi et al., 1994; Nishikimi et al., 1988), as well as in bats of the genus Pteropus (Cui et al., 2011).

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