ABSTRACT
M. Kruatrachue et al. have shown that the red blood cells with a deficiency of glucose-6-phosphate dehydrogenase (G6PD) have fewer malaria parasites. The logic of an explanation of the frequencies of the red cell defects begins with the question: Why do high frequencies of these deleterious genes exist? Since the selection against hemoglobins C and E and the G6PD deficiency is much less than that against hemoglobin S, the selective advantage of their respective heterozygotes is also much less. Hence for these genes the difference between the two outcomes of any definitive experiment will be far less than that for hemoglobin S. If a population with a high frequency of one of the red cell defects were found and it had no history of malaria, this would be concrete evidence that other selective forces besides malaria are involved.
