Dissertation Research: Epistatic Genetic Variation in Quantitative Characters

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Genetic techniques will be used to test the effect of genes extracted from a wild population of Drosophila melanogaster in two different genetic backgrounds for characters that are often assumed to be controlled by independently acting genes. The experiments are also designed to get information about the nature of gene interaction among variable genes in natural populations. The primary significance of this work is its relevance to basic research in population genetics and evolutionary theory, in which it is commonly assumed that genes which determine the value of morphological characters such as the size or length of structures, act independently of each other, so that the change that any one gene produces does not depend on other genes. However, results from selection experiments in the laboratory, as well as gene interaction studies, have shown that the effect of any one gene often depends on other genes; that is, what is usually referred to as the genetic context or background. Because the rate of evolution depends on the magnitude of genetic variation, a comprehensive understanding of the evolutionary process requires a more complete understanding of the extent to which gene interaction affects the amount of variation in the characteristics of organisms. Artificial selection, the chief means of selectively breeding improved strains of domestic plants and animals, similarly depends on the amount and kind of genetic variation in desirable characteristics. It is known that an optimal breeding program depends on the extent to which gene interactions affect a desirable characteristic. This research also explores a method of assessing the magnitude of such gene interactions.