A GENERAL MODEL TO ACCOUNT FOR ENZYME VARIATION IN NATURAL POPULATIONS

John H. Gillespie ¹ and Charles H. Langley ²

¹ Department of Biology, University of Pennsylvania, Philadelphia, Pennsylvania 19174
² University of Wisconsin, Department of Medical Genetics, Madison, Wisconsin 53706

Approximate conditions for genetic polymorphism in temporally and spatially varying environments are presented for loci which are intermediate at the level of fitness or at the level of gene function. The conditions suggest that polymorphism will be more likely in more variable environments while unlikely in constant environments. Biochemical evidence is presented to justify the assumption of heterozygote intermediacy. Observations on natural populations are cited which substantiate the claim that allozymic polymorphism is primarily due to selection acting on environmental variation in gene function.