The evolution of the globin gene family in humans

The globin gene family evolved from a single ancestral globin gene. The first gene duplication produced two genes that accumulated mutations and became the genes encoding myoglobin and the family of hemoglobins. The modern myoglobin gene is found on chromosome 22. An ancestral hemoglobin gene duplicated to produce the ?- and ?-globins. Further duplications of ancestral ?-globin and ?-globin genes produced several homologous genes on chromosomes 16 and 11, respectively. The four genes shown in grey are nonfunctional pseudogenes.