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Types of signals

Inducer. Responder. Types of signals. Setting up a signaling gradient: the role of the wingless gene. Anterior. A- Hair. segment. P- Bare Skin. Cells know their positions within the body and differentiate accordingly. Posterior.

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Types of signals

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  1. Inducer Responder Types of signals

  2. Setting up a signaling gradient: the role of the wingless gene

  3. Anterior A- Hair segment P- Bare Skin Cells know their positions within the body and differentiate accordingly Posterior

  4. To set up this pattern, flies use the secreted protein Wingless to specify a posterior fate A = hair P = bare skin segment wild type

  5. Anterior: Low Wingless, Hairs Posterior: High Wingless, Naked Cuticle

  6. Signals can also act in a graded fashion

  7. Wingless diffuses away from the cells that secrete it Wingless-expressing cells

  8. Wingless signaling specifies posterior cell fates in the ventral epidermis A = hair P = bare skin wild type arm mutant ALL cells have anterior (hair) fate

  9. Therefore, all cells can see wingless, and the concentration of wingless itself is what determines cell fate Setting up a signal gradient

  10. Signal transduction moves information from the cell surface to the nucleus and other cellular targets

  11. Genetics revealed the ligand and proteins in this signal transduction pathway

  12. Genetics can also position proteins within the signaling pathway

  13. An example of the conservation of key developmental regulatory machinery across animal phyla flies mammals See also Figure 6.20A

  14. Colon cancer, the second leading cause of cancer deaths in the U.S., results from inappropriate Wnt signaling Polyps, the first stage In tumor development

  15. Long range signaling Insects: A model system to study hormonal control of postembryonic development Figure 18.9

  16. Vincent B. Wigglesworth Discovered that blood-borne hormones control insect metamorphosis through experiments with a blood-sucking bug, Rhodnius prolixus

  17. Experiment #1 Blood-borne hormones regulate the timing of metamorphosis induces 1st instar larva to molt into very small adult

  18. Other hormones prevent metamorphosis Experiment #2

  19. Other hormones prevent metamorphosis Experiment #3 Transplant corpus allatum from 4th to 5th instar larva Adult Result: blocks metamorphosis, instead get “6th instar larva”

  20. PTTH The cascade of hormones regulating insect metamophosis 20E Figure 18.16

  21. Steroid hormones (ie 20E): hydrophobic signaling molecules that can pass through the plasma membrane 20E

  22. Most signals Steroid hormones (ie. 20E)

  23. An insecticide produced by plants cause premature metamorphosis

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