Linkage disequilibrium in a local population of Drosophila melanogaster.

461 second chromosomes of Drosophila melanogaster were extracted from a Raleigh, N.C. population and four enzymes controlled by the genes located in this chromosome (alcohol dehydrogenase (EC 1.1.1.1.), malate dehydrogenase-1 (EC 1.1.1.37), glycerol-3-phosphate dehydrogenase-1 (EC 1.1.1.8), and alpha-amylase (EC 3.2.1.1), were assayed electrophoretically and cytologically (salivary-gland chromosomes). Linkage disequilibrium could not be detected among any pair of isozyme genes, except in one case that is best explained as due to a chance error in estimation. Some disequilibria were detected, however, between isozyme genes and polymorphic inversions. The relative viabilities of homozygous and heterozygous combinations of these chromosomes were estimated with respect to the alcohol dehydrogenase alleles and the glycerol-3-phosphate dehydrogenase alleles; no significant difference could be detected. The role of epistasis in natural populations is discussed on the basis of these results.