Abstract
The rate of synthesis of δ-aminolevulinate dehydratase in mice is controlled by alleles at the levulinate (Lv) locus. Two structural mutations modifying the sensitivity of δ-aminolevulinate dehydratase to heat have been identified. Genetic analyses established that the structural locus for δ-aminolevulinate dehydratase was either physically close to or identical with the locus that controls its rate of synthesis.