Virtually every animal and plant species exhibits genetic variation for a variety of enzymes involved in the control of metabolism. Although a few cases have been studied in detail, we have a very poor understanding of the biological significance of this variation. Over the past two years, studies on a variety of plant and animal species have demonstrated that the level of individual genetic variation, estimated for a series of enzyme synthesizing loci, is positively correlated with energy balance. The higher the level of individual genetic variation (i.e., heterozygosity), the lower the cost of metabolism, measured as heat production or mass-specific rates of oxygen consumption. The proposed research will attempt to establish a causal link between genetic variation of metabolic enzymes and this phenotypic variation in energy balance. The key to this problem seems to lie in how genotype influences the rate of enzyme synthesis and degradation and the energy cost associated with each. The proposed research will use enzyme specific antibodies and a variety of radioisotopes to estimate the metabolic costs of synthesis and degradation for a series of specific enzymes and how these costs are mitigated by genotype at the enzyme synthesizing loci. The results will be of significance in a variety of areas ranging from evolutionary biology to animal and plant breeding.
