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Environmental and genetic influences on the life span of adult Drosophila melanogaster Richter, Murray Dean


The onset of senescence and the rate at which organisms age are influenced by both extrinsic and intrinsic factors. Extrinsic factors include temperature, humidity and diet. Intrinsic factors arise within an organism as a result of normal metabolism. An example is the production of free radicals, highly reactive compounds that usually arise as byproducts of normal oxidative functions. Another less commonly considered instrinsic factor is the genetic makeup of an organism. Not only do different species have different characteristic life spans, but different strains within a species also have different characteristic life spans. This study examines how environmental and genetic differences affect the adult life span of Drosophila melanogaster. Drosophila was chosen because of its well characterized genetics, the ease with which it can be cultured and its life span measured, and the ability to control environmental conditions, particularly temperature. The study used three different approaches. The first approach looked at the influence of preimaginal development on adult longevity. The duration of development of melanogaster was altered using developmental temperature shifts. Both a wild-type strain and a mutant strain that displays a longer developmental period at 29°C than at 22°C were examined. No correlation was found between developmental duration and adult life span in either strain. The second approach examined the differences in adult longevity that existed between a highly inbred laboratory strain and four strains recently isolated from the wild. This was done to assess the suitability of highly inbred strains for studying aging. The laboratory strain showed much less variation in life span than did any of the recently isolated strains. The third approach looked at the possible roles of DNA damage accumulation and DNA repair in controlling life span in Drosophila. Mutagen-sensitive (mus) mutants representing strains that are potentially defective in DNA repair were examined to see if their life spans were altered relative to control strains. Little difference was found between mus strains and the controls. Where differences did exist, it was not clear that they were a direct result of defective repair in the adult. The results of each approach are discussed with respect to current knowledge of the processes controlling aging and senescence in Drosophila and other organisms.

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