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Drosophila melanogaster

Explore the natural history, life cycle, and utility of Drosophila melanogaster as a model organism in genetic, developmental, and molecular biology research. Learn about its origin, gene distribution, shared biology with humans, gene disruption projects, applications in disease modeling, and future prospects.

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Drosophila melanogaster

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  1. Drosophila melanogaster Source: Zdenék Berger

  2. Mating adult Egg-laying Life Cycle (10 days) pupa Embryo larva

  3. Drosophila natural history • Originated in Africa • Probably spread by human activity • Now found most places where we live • Likes compost, rotting fruit, yeast • Some features conserved, others a reflection of its life strategy • Harmless (mostly) • Most lab strains derived from isolates collected before 1940’s • Strains collected subsequently have P transposable elements and can’t easily be used

  4. E. coli Yeast Worm Fly Mouse Human Genome (Mb) 4.6 12 150 3000 3000 100 # Genes 4000 6000 19000 15000 30000? 30000? 11 5 # Neurons 0 (1) 302 10 10 Model Organisms - a trainspotter’s guide

  5. Where our pet flies live… Mice - 75c/day 150k$/yr Flies ~ 20k$/yr (consumables and labour) Can’t be stored frozen :-( Source: John Roote

  6. What are flies useful for?

  7. Fly pushing Early 1900’s - Drosophila contributes to our understanding of heredity Mid 1900’s - Grows in popularity among developmental biologists Homozygous lethal mutations can be kept indefinitely as heterozygous balanced stocks 1970’s - 1980’s - Molecular biology, cloning of Hsp, Hox 1970’s - 1980’s - Large screens for developmental mutants 1982 - Transformation by injection of marked P transposable element into syncytial embryos; transgenic flies identified by marker in F1 1988 - Easy mobilisation of P made possible by stable transposase-producing strains

  8. Recent articles from PubMed

  9. C.J. O’Kane (2003). Seminars in Cell and Developmental Biology 14:3-10. Source: Claude Everaerts

  10. What’s different? • More gene redundancy in humans & mammals • Some organisation of tissues and organs • Cardiovascular system • Acquired immunity (antibody response) • We’re studying them, instead of them studying us

  11. Insertional mutagenesis: many ways to kill a gene…

  12. Fly Gene Disruption Projects • Based on transposable element insertion • Allows further local mutagenesis • Non-directed - like Venter’s sequencing strategy • Not random • ~ 15000 target genes • include ~ 4000 vital genes • Requires ~ 1 insertion per 8 kb • Coverage perhaps 25% of that, more on their way into public domain

  13. FlyBasewww.flybase.org

  14. Other ways to make “mutants” • EMS - still has its attractions • Targeted knockouts for reverse genetics • Imprecise excisions for reverse genetics • RNAi for reverse or forward genetics • Deletion kits in defined backgrounds • Ask a fellow flypusher

  15. Getting round early lethality • GAL4 x UAS-X for targeted expressionCan be used for regulated RNAi expression

  16. GAL4 enhancer traps

  17. Getting round early lethality • GAL4 x UAS-X for targeted expression • Enhancer/suppressor screens

  18. Identifying genes in receptor tyrosine kinase signalling - screening for enhancers of sevenlessts

  19. Getting round early lethality • GAL4 x UAS-X for targeted expression • Enhancer/suppressor screens • Mitotic clones (using FLP recombinase)

  20. Mutant screens using mitotic clones

  21. Getting round early lethality • GAL4 x UAS-X for targeted expression • Enhancer/suppressor screens • Mitotic clones (using FLP recombinase) • Temperature-sensitive point mutations • RNAi screens in cultured cells

  22. Shared biology - shared diseases • Cancer • Ageing • Neurodegeneration • Infectious disease • Models for disease vectors • Behaviour

  23. Flies and “your” disease • Do flies have disease-gene homologs? • Do flies have basic cellular processes related to the disease? • Be nice to a friendly fly geneticist

  24. The future? • More insertions • UAS-RNAi collections • SNPs, better mapping of point mutations • Temperature-sensitive alleles for cell biology • Screens take more work in flies than in worms • Some things only possible in flies and not worms - physiology, some development, some cell biology • “Hopping in” takes about $20k investment, or a friendly fly lab to drop in on

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