Subunit molecular weight and genetic variability of proteins in natural populations

The relationship between subunit molecular weight and heterozygosity was studied in six different groups of organisms, i.e., 9 species of primates, 32 species of rodents, 56 species of reptiles, 12 species of salamanders, 64 species of teleost fishes, and 29 species of Drosophila. The correlation coefficient between them was positive in all groups, and the magnitude of correlation was roughly in agreement with the theoretical expectation under the mutation-drift hypothesis when the incomplete correlation between molecular weight and mutation rate was taken into account. Furthermore, the correlation was higher when the average heterozygosity was high than when this was low, as theoretically expected.