Beta Globin Sequences
The alpha and beta globins, which combine to form the hemoglobin (image left) of red blood cells, are members of a large and ancient multigene family. The common function of the globins is to bind oxygen. Each of the four chains ( two alpha, two beta) of hemoglobin can bind one oxygen molecule. Although some amino acid substitutions in the beta globin sequence can render the molecule nonfunctional (as in sickle-cell anemia), many others are tolerated, and have accumulated over the millions of years that separate the major lineages of the placental mammals. These changes can be seen as improvisational riffs by different species on the basic beta globin sequence. |