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BIO310: Developmental Biology

Unit 5: Axis Formation   All eggs have essentially radial symmetry, but most animals exhibit at least some bilateral symmetry: differences in their right and left sides, their anterior and posterior ends, as well as their dorsal and ventral surfaces.  How are these patterns created?  They are the result of a complex series of processes that specify which cells will be in which part of the embryo and that in turn guarantee that the organism’s heart will be in the right place—literally.  In this unit, you will focus on axis formation in two model systems: an invertebrate (the fruit-fly, or Drosophila spp.) and a vertebrate (the frog).  These organisms have been studied extensively, and the molecular mechanisms of their axis formation are relatively well understood.  They will accordingly serve as excellent illustrations of the complex processes involved in this aspect of development.

Unit5 Learning Outcomes
Upon successful completion of this unit, students will be able to:

  • Demonstrate an understanding of the importance and role of the Organizer in axis formation and patterning.
  • Recognize and identify some of the major genes and proteins involved in various types of axis formation.
  • Demonstrate an understanding of the steps of the gastrulation process and the roles of major genes and proteins in that process.

5.1 Types of Axes   - Reading: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “An Introduction to Early Development” Link: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “An Introduction to Early Development” (HTML)
 
Instructions: Read the subsection on “Axis Formation” its entirety, along with Figure 8.7. This will cover the material in 5.1.
 
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5.1.1 Dorsal-Ventral   5.1.2 Anterior-Posterior   5.1.3 Left-Right   5.2 Axis Formation in Drosophila   - Reading: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “Snapshot Summary: Drosophila Development and Axis Specification” Link: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “Snapshot Summary: Drosophila Development and Axis Specification” (HTML)
 
Instructions: Read this summary in its entirety. It will provide a greater overview of the processes addressed in your specific readings for 5.2.1-5.2.2.
 
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5.2.1 The Anterior-Posterior Axis   - Reading: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “The Origins of Anterior-Posterior Polarity” Link: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “The Origins of Anterior-Posterior Polarity” (HTML)
 
Instructions: Read the introductory paragraph of this section along with Fig. 9.8.
 
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5.2.2 The Dorsal-Ventral Axis   - Reading: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “The Generation of Dorsal-Ventral Polarity” Link: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “The Generation of Dorsal-Ventral Polarity” (HTML)
 
Instructions: Read the introductory paragraph of this section and the subsection “The Morphogenetic Agent for Dorsal-Ventral Polarity” along with Fig. 9.33.
 
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5.3 Axis Formation in Amphibians   - Reading: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “Axis Formation in Amphibians” Link: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “Axis Formation in Amphibians” (HTML)
 
Instructions: Read all of this section, including associated figures, except for the subsection “Snapshot Summary.” This will cover the material in 5.3.
 
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  • Reading: DNATube: HHMI’s “Spemann’s Organizer” Link: Web Media: DNATube: HHMI’s “Spemann’s Organizer” (Adobe Flash)
     
    Instructions: Watch this brief (approx. 2 minutes) video about the seminal experiments Spemann and Mangold conducted to learn about the mechanisms of embryonic patterning.
     
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5.3.1 The Nieuwkoop Center   5.3.2 Spemann’s and Mangold’s Experiments: The Organizer   5.4 Overview of Axis Formation in Other Major Groups   5.4.1 Birds   - Reading: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “Early Development in Birds” Link: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “Early Development in Birds” (HTML)
 
Instructions: Read all of the subsection on “Axis Formation,” along with associated figures (Figs. 11.13-11.19).
 
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5.4.2 Mammals   - Reading: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “Early Mammalian Development” Link: The National Institutes of Health: Professor Scott Gilbert’s Developmental Biology: “Early Mammalian Development” (HTML)
 
Instructions: Read all of “Anterior-Posterior Axis Formation” and “The Dorsal-Ventral and Left-Right Axes” along with associated figures (Figs. 11.34-11.44).
 
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