Genetic background and the fitness of allozymes.

Experimental perturbations of gene frequency at the esterase-5 locus in Drosophila pseudoobscura were carried out in a series of population cages started with differing numbers of founder chromosomes. Cages founded with few chromosomes showed changes in gene frequency at the allozyme locus. Such changes were less marked in cages founded with a larger sample of chromosomes. These experiments show the importance of linkage disequilibrium in affecting allozyme frequencies, and emphasize the necessity of careful experimental design when studying fitness differences between allozymes in laboratory populations.