Bio 113P Lab 4: Effects of Wolbachia Infection on the Offspring Sex Ratio of Nasonia, vitripennis

Bio 113P Lab 4: Effects of Wolbachia Infection on the Offspring Sex Ratio of Nasonia, vitripennis

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Effects of Wolbachia Infection on the Offspring Sex Ratio of Nasonia vitripennis Manuel Vazquez 4/14/2012
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Introduction: As previously described in Ph e no t ypi c E ff ec ts o f Wolba c hia on t h e R e produ c t iv e B e havior s and Ou t c o m e s o f Na s onia Vi t rip e nni s (Vazquez 2, 2012), Wolba c hia is an endosymbiotic bacteria that lives as a reproductive parasite in a large fraction of insect species worldwide. In order to be passed on to future generations, the infection must be present in the eggs of the mother, since it lives in the cytoplasm of the cells of the reproductive system, but most of the cytoplasm is removed from the sperm cells during development ± thus, the infection is only inherited via the mother. This means that it is most favorable for Wolba c hia to be present in females, and for the offspring of a pairing of insects to be mostly or all female as well. To this end, the parasitic bacterium has various methods of subterfuge which can be used to hijack the reproductive systems of its host. Na s onia vi t rip e nni s , one such host of the bacterium, reproduces through a haplo-diplo mating system, where an unfertilized female will lay haploid offspring, which will result in males, and where a fertilized female will lay diploid offspring, rearing more females. Wolba c hia , however, interferes with this normal cycle by four main mechanisms of disruption: feminization, male killing, parthenogenesis, and cytoplasmic incompatibility (CI). In CI, the sperm of infected males and uninfected females, or of females infected with a different strain of Wolba c hia , are rendered incompatible with one another due to Wolba c hia ¶V LQWHUIHUHQFH ZLWK WKH GHYHORSPHQW RI the gametes, resulting in a failure of fertilization, and thus in all-male broods; in contrast, in parthenogenesis, unfertilized females will develop diploid eggs which in turn form all-female broods from unfertilized eggs. Male killing is the result of successful copulation, whereby Wolba c hia -infected haploid eggs are killed by the infection itself, leaving only diploid eggs in the brood, and thus resulting in an all-female, but much smaller than normal, filial generation; this presumably serves the purpose of reserving all the available resources for the diploid female
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