Hemoglobins A and A 2 in New World Primates: Comparative Variation and Its Evolutionary Implications

Abstract
Hemoglobin A 22 δ 2 ) in New World primates represents about 1/160 to 1/16 of total hemoglobin and, by virtue of this low proportion, is presumed to be functionally unimportant. Nonetheless, A 2 exhibits genetic polymorphism by electrophoresis in three out of five genera, whereas the major component, hemoglobin A (α 2 β 2 ), is electrophoretically invariant. Moreover, in four genera, including man, the evolutionary accumulation of mutations has been greater in δ than in β. Such findings suggest that both polymorphism and evolutionary changes can accrue to an effectively functionless and thus selectively nearly neutral gene.