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Bio318 Final Presentationn

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Bio318 Final Presentationn

  1. 1. Does Altruism Differ BetweenIsogenic and Unrelated Fruit Flies? Cigdem Demirez Soham Bhatia Bio318Y http://www.littlebrownbooks.net/sedaris/ March.20.2012
  2. 2. Altruism, Kin Selection and Indirect Fitness• no study on Drosophila•Altruism = sacrificial1•Kin selection: favour relatives2•Indirect fitness: benefits selfthrough relatives3 http://www.shutterstock.com/pic-14703082/stock- photo-male-common-fruit-fly-drosophila- melanogaster1- Kropotkin, Peter. (1902). Mutual Aid: A Factor of Evolution.2- Darwin, Charles. (1859). Origin of Species.3- Hamilton, W.D. (1964). The Genetic Evolution of Social Behaviour. J. of Theo. Bio. 7 (1): 1-16.
  3. 3. Drosophila melanogaster•Wild type -Isogeny: +; BB; +BB•Sexually Dimorphic -easy to differentiate sexes•Short life cycle: -20 to 30 days4 -can study many generations Amsel, Sheri. www.exploringnature.org
  4. 4. Do fruit flies share more with geneticallyidentical versus unrelated flies, if at all? Hypothesis: Fruit flies will show greater altruism in sharing food, if at all, towards genetically identical individuals (isogenic) than towards unrelated individuals. Prediction: If Drosophila are altruistic, a pair of isogenic flies will statistically differ less in time spent at food source in comparison to an unrelated pair.
  5. 5. Experimental Protocol1- Rear Flies2- Experimental trials: 5 groups• pair of: isogenic males isogenic females unrelated males unrelated females•Control: single males & females3- Record Measurements• time spent at food source within 5 minutes
  6. 6. 1- Rearing Flies Isogenic M Strain and C Strain 9 families each5 •Sucrose based food •21 ºC •12h light/dark cycle •Relatively humid5-Simon, A.F. et. al. (2012). A simple assay to study social behaviour in Drosophila: measurement ofsocial space within a group. Genes Brain and Behaviour. 11(2): 243-252.
  7. 7. 2- Experimental TrialsIsogenic Group: n=30 pairs of - males - females •15 pairs for each strainUnrelated Group: n=30 pairs of - males - femalesControl Group: n=30 single - males - females
  8. 8. 3- Measurement•Food deprive for 24 h•Pair similar flies•Measure time spent at food source by each fly•5 minute trials•Time of day: 11 a.m. - 3 p.m.•Assumptions - each fly equally interested to feed
  9. 9. Analyzing Variables•Independent variable: Categorical: -level of relatedness -gender•Response variable: Continuous: time spent at food source•Statistical Test: non-parametric: Mann-Whitney U test
  10. 10. No difference in sharing betweengenetically identical and unrelated flies 200 180 Avg Difference in Time 160 140 120 male 100 female 80 60 40 20 0 control isogenic unrelated
  11. 11. No significance in Values Male Female U = 538 U = 538 Isogenic vs Unrelated P = 0.207 P = 0.193 U = 470 U = 499 Isogenic vs Control P = 0.476 P = 0.312 U = 380 U = 407 Unrelated vs Control P = 0.225 P = 0.312All p-values > α (0.05)All U-values > Ucrit (317)
  12. 12. Conclusion: No difference in sharing between genetically identical and unrelated flies Hypothesis: Fruit flies will show greater altruism in sharing food, if at all, towards genetically identical individuals (isogenic) than towards unrelated individuals. Prediction: If Drosophila are altruistic, a pair of isogenic flies will statistically differ less in time spent at food source in comparison to an unrelated pair.
  13. 13. Why did our predictions fail?1- No knowledge of the degree to how geneticallyunrelated strains are2- Variation in attraction to food3- Spatial factor
  14. 14. Alternative Hypotheses 1- Flies do not have the sharing behaviour because they are genetically adapted to being exposed to ample food resources 2- Drosophila were not eating to conserve food6- Kent, C. et. al. (2009). The Drosophila foraging gene mediates adult plasticity and gene-environment interactions in behaviour, metabolites and gene expression in response to fooddeprivation
  15. 15. ConclusionsDrosophila not shown to share more with genetically identical flies than unrelated flies http://images.ask.com/fr?q=fruit+fly+i n+lab&desturi=httpbwidth

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