Dr. Steven Mount plans to study the mechanisms whereby a second mutation in the genome of Drosophila melanogaster acts to suppress the phenotypic effects of a first mutation caused by the insertion of a transposable element into a previously functional gene. Specifically, he will utilize the color of the eye of the fruit fly (normally red) as a means of following genetic changes. When the transposable element, copia, inserts into the white gene, the eye color becomes an apricot hue. A specific mutation at a second and different gene causes a reversion to the normal eye color red. What is the mechanism(s) utilized by Drosophila which effects that reversion? These experiments are directed at understanding the basis of extragenic suppression in drosophila. Most suppressible mutants in drosophila appear to arise from the insertion of a transposable element. Thus, although the phenomenon is superficially similar to suppression in bacteria, the kinds of mutants that can be suppressed, and the mechanism for doing so, differ in fundamental way from those seen in prokaryotic systems. The clarification of the molecular basis of suppression in bacteria provided important insight into the nature of the genetic code and the mechanism of translation; it seems likely that the molecular details of suppression in drosophila will provide similar insight into tissue-specific regulation of gene expression and post- transcriptional modification of mRNA.
