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Genetic Model Organisms

mouse. worm. Genetic Model Organisms. fish. yeast. fruit fly. weed. Drosophila melanogaster Genetics and Developmental Biology Physiology and Behavior Many disease-causing genes in humans have corresponding homologues in the fly genome Cancer Neurodegenerative disease

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Genetic Model Organisms

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  1. mouse worm Genetic Model Organisms fish yeast fruit fly weed

  2. Drosophila melanogaster Genetics and Developmental Biology Physiology and Behavior Many disease-causing genes in humans have corresponding homologues in the fly genome Cancer Neurodegenerative disease Drug addictions Diabetes Obesity

  3. Life cycle of Drosophila • embryogenesis • three larval stages • a pupal stage • the adult stage

  4. Groups of cells called imaginal discs are set aside at specific sites in the larval body. From these the various body parts develop during pupation (adult muscle, the nervous system, etc).

  5. Advantages of the fly system • A relatively short life cycle (10 days) • Culturing flies is cost-effective (vs mice) • A variety of genetic and molecular tools available (functional testing in vivo) • Complete genome sequence (13,500 genes)

  6. Advantages of the fly system • A relatively short life cycle (10 days) • Culturing flies is cost-effective (vs mice) • A variety of genetic and molecular tools available (functional testing in vivo) • Complete genome sequence (13,500 genes)

  7. Thomas H. Morgan and the Caltech fly group • Bridges (left) and Sturtevant in 1920  • (B) Morgan in 1917

  8. Christiane Nüsslein-Volhard, Eric Wieschaus and the Baden fly group (1980) Nüsslein-Volhard and Wieschaus (along with Edward Lewis) were awarded the 1995 Nobel Prize for Physiology/Medicine.

  9. Saturation Mutagenesis Screen and the Segmentation Hierarchy

  10. Biological question Screening assay Speed Specificity Lead to biological insight?

  11. Time table of embryogenesis

  12. Drosophila embryogenesis 3 h pole cells (germ line) Cellular blastoderm Anterior Posterior 10 h Segmented embryo 22 h 1st instar larva

  13. Mutant bicoid embryo a b

  14. Mutations insegmentation genes

  15. Segmentation Hierarchy Maternal genes Gap genes Pair rule genes Segment polarity genes

  16. Molecular Cloning of Genes

  17. Molecular Mechanisms What is the gene product? Where and when is it active? Was the genetic prediction correct?

  18. Segmentation fate map of Drosophila embryo

  19. Drosophila early development

  20. ftz (fushi tarazu) gene expression pattern in situ hybridization (RNA detection) need probe! Ernst Hafen and Walter Gehring (1983)

  21. even-skipped (blue), ftz (red) antibody staining (protein detection) need antibody!

  22. Gap Genes hunchback (blue) and Krueppel (green) Fluorescent staining

  23. Molecular patterningof the embryo Bicoid (blue) Even skipped (red) Krüppel (yellow)

  24. Segmentation Hierarchy

  25. Biological question Screening assay Speed Specificity Lead to biological insight?

  26. Germ-line Transformation and in vivo Genetic Manipulations

  27. For example... Is the striped expression of ftz really necessary? What happens if you express ftz everywhere? How would you test this?

  28. Transposase (“helper”) plasmid acts on P-element ends for integration into genome 2 transformation Heat shock promoter-ftz P-element plasmid 1 ftz Adapted from Wang and Lin, 2004

  29. Syncitial blastoderm Germ cells Transposable P-element mediated transformation Allan Spradling and Gerald Rubin (1982)

  30. Drosophila embryogenesis 3 h pole cells (germ line) Cellular blastoderm Anterior Posterior 10 h Segmented embryo 22 h 1st instar larva

  31. The UAS-Gal4 System: How you can make flies with eyes on their legs

  32. Gal4 x promoter Gal4 UAS gene Regulating Gene Activity with Pinpoint Precision progeny flies will express gene in the place of choice

  33. wild-type Misexpression of eyeless using the UAS-Gal4 system

  34. Polytene chromosomes Specialized chromosomes Discovered by Balbiany in 1881 in salivary gland of drosophila larva (3rd instars) Why salivary gland of drosophila larva will have Polytene Chromosomes????????????????

  35. Drosophila Karyotype Drosophila Polytene chromosome

  36. 1933, Painter showed the banding pattern in Drosophila 1935, Bridges Banding pattern is fixed in a particular chromosome in a particular species

  37. Polytene chromosome is found in 3rd instar larva of Diptera Also found in Malpighian tubules Mid Gut epithelium Rectum Of Diptera order of insects And in ovary of some plants

  38. wildtype obese (leptin)

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