Protein Polymorphism

Abstract

IN their well known study of protein polymorphism in Drosophila pseudoobscura, Prakash, Lewontin and Hubby¹ showed that most loci reveal little or no differentiation in allele frequencies in different sub-populations; they concluded that the observed polymorphisms cannot be due to random genetic drift of neutral mutations and are most likely to be caused by some form of balancing selection. This conclusion has been challenged by Kimura and Ohta² on the grounds that only a small amount of migration between the sub-populations is required to make them into an effectively single panmictic population in which one would not expect to find much local differentiation in allele frequencies under the neutral mutation theory originally proposed by Kimura³. The purpose of this letter is to point out another feature of the data of Prakash et al.¹ which suggests that the polymorphic alleles are not selectively neutral.