Molecular Heterosis for Heat-Sensitive Enzyme Alleles

Heat denaturation studies were carried out and revealed hidden genic variants with the same net charge at the Octanol dehydrogenase-1 locus in Drosophila pseudoobscura. Studies of several genetic crosses between strains with different heat-sensitivity alleles showed that the F₁ retained more in vitro enzyme activity after being heat-treated for a specified amount of time at a given temperature than the heat-resistant parent. We call this phenomenon "heterosis for heat-stability of enzyme activity" and discuss its possible molecular mechanism, its relation to maintenance of genetic variation in natural populations, and its bearing on the "classical" and "balance" hypotheses.