Drosophila pseudoobscura

…populations of the vinegar fly Drosophila pseudoobscura, he found extensive genetic variability. Furthermore, about 1940 evidence accumulated that in a given local population some genes would regularly change in frequency with the seasons of the year. For example, a certain gene might appear in 40 percent of all individuals in…

In the vinegar fly Drosophila pseudoobscura, for example, three genotypes exist at the gene locus that codes for the metabolically important enzyme malate dehydrogenase—the homozygous SS and FF and the heterozygous SF. When the SS homozygotes represent 90 percent of the population, they have a fitness about two-thirds that…