UBC Theses and Dissertations
Longevity, behaviour, and mapping of three temperature sensitive adult lethal alleles of Drosophila melanogaster Hansen, Beverley Nina
The rate at which an organism ages, as well as the onset of senescence are determined by many factors. Different species, as well as different strains of the same species, have characteristic lifespans. This study is an investigation of three strains of Drosophila melanogaster, to test their influences on ageing and senescence. Temperature-sensitive putative allele mutants [formula omitted], [formula omitted], and [formula omitted], and wild-type Oregon-R (control) Drosophila melanogaster were examined for patterns of age dependent behaviour loss over the course of their adult lifespans. Longevity, geotaxis, phototaxis, and motor activity were examined at both the permissive temperature, 22°C, and the restrictive temperature, 29°C. [formula omitted] displayed a longevity and behaviour loss pattern similar to the wild-type strain at 22°C. At 29°C, longevity was significantly reduced compared to wild-type, and the pattern of age-dependent behaviour loss was compressed into a shorter time frame. This pattern of behaviour loss was consistent with that expected from a mutation which increases the rate of ageing (Leffelaar and Grigliatti, 1984). The lifespan of [formula omitted] at 22°C was reduced, when compared with Oregon-R, but the behaviour loss pattern was similar. At 29° C the flies died rapidly, with almost total, immediate, behaviour loss. Survival curves at 22°C, 25°C, and 29°C adjusted for the rate of living were coincident. Flies of the type [formula omitted], isolated in a separate screen as flight-reduced, demonstrated differences from [formula omitted] and [formula omitted] in longevity curve shape as well as behaviour. Lifespan was reduced at both 22°C and 29°C, and although behaviour differed slightly in young flies, the behaviour loss pattern was similar to that of [formula omitted]. The order of severity of effects of the restrictive temperature from the least affected allele to the most affected was [formula omitted], [formula omitted], and [formula omitted]. At 22°C, hybrid flies of type [formula omitted] / [formula omitted] and [formula omitted] / [formula omitted] exhibited lifespans comparable to Oregon-R, the latter being longer lived than either parental strain. The hybrid strain [formula omitted] / [formula omitted] was demonstrated to have longevity intermediate between parent types, and reduced with respect to Oregon-R. Geotactic behaviour was reduced in all three hybrids at 22°C, but phototaxis and motor activity were similar to that of wild-type flies. At 29°C all hybrid strains could be said to demonstrate intermediate lifespan, between females of the generating parent strains. Complementation did not occur, and thus all mutants under study were confirmed to be alleles. Behaviour was reduced in [formula omitted] / [formula omitted] and [formula omitted] / [formula omitted] at 29°C, but not in [formula omitted] / [formula omitted]. Flies of type Deficiency/mutant were found to have greatly reduced lifespans at both 22°C and 29°C. The order of severity of effects was Df/[formula omitted], Df/[formula omitted], and Df/[formula omitted], with the last being the most severely affected, with deformities noted at both temperatures. This result confirms the cytological location of these mutants relative to their genetically determined position. The focus of action of the mutant gene [formula omitted] was mapped two ways by means of gynandromorph analyses. The drop-dead behaviour was mapped against a background map constructed for this study. This behaviour appears to map to the ventral thoracic region, and most likely involves presumptive mesodermal tissue. The paralysis behaviour noted in these flies at 29°C was then mapped separately for each leg. Three foci were found. All three appear to map to presumptive nervous tissue. Involvement of nerve and muscle tissues would not be surprising, considering the behaviours noted earlier. The discussion involves speculation as to the precise function of all three [formula omitted] genes.
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