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Early Development - PowerPoint PPT Presentation

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Early Development . Selected Invertebrates. Cleavage. What characterizes this process?. Cleavage. How does the cell cycle of blastomeres compare with that of somatic cells?. Cleavage. What happens to the embryo during the mid-blastula transition? When does this occur?. Cleavage.

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Early development l.jpg

Early Development

Selected Invertebrates

Cleavage l.jpg

  • What characterizes this process?

Cleavage3 l.jpg

  • How does the cell cycle of blastomeres compare with that of somatic cells?

Cleavage4 l.jpg

  • What happens to the embryo during the mid-blastula transition?

  • When does this occur?

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  • What is karyokinesis and cytokinesis and how do they compare?

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  • What influences the pattern of cleavage in a particular organism?

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  • How are cell fates specified during cleavage?

    • cell-cell interactions

    • asymmetric distribution of morphogenic determinants

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  • What characterizes gastrulation in organisms?

  • What kinds of movements occur?

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Axis Formation

  • What are the three major body axes?

Sea urchin development l.jpg
Sea Urchin Development

  • What does the cleavage pattern look like?

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Sea Urchin Development

  • What characterizes the blastula stage?

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Sea Urchin Development

  • At what stage are the fates of individual cells determined?

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Sea Urchin Development

  • What role does β-catenin play in specification?

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Sea Urchin Development

  • When does axis specification occur?

    • animal-vegetal axis established before fertilization

    • anterior-posterior axis determined by a-v axis

      • vegetal – determinants for posterior development

    • dorsal-ventral and left-right after fertilization

      • d-v by first cleavage plane

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Sea Urchin Development

  • How does gastrulation begin?

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Sea Urchin Development

  • What appears to be responsible for the ingression of primary mesenchyme?

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Sea Urchin Development

  • What appears to be responsible for the initial invagination that occurs during gastrulation?

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Sea Urchin Development

What is the fate of these vegetal plate cells?

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Sea Urchin Development

  • What happens during later stages of invagination?

Snail development l.jpg
Snail Development

  • What kind of cleavage pattern characterizes these animals?

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Snail Development

  • Orientation of cleavage plane determines right or left coiling snails

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Snail Development

  • What appears to be responsible for the mosaic development seen in molluscs?

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Snail Development

  • What is the polar lobe and why is it important?

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Snail Development

  • Why does removal of the D blastomere or its first or second derivatives result in incomplete larvae?

  • If D blastomeres don’t directly contribute cells to formation of many structures why are they so important to the formation of the same structures?

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Snail Development

  • What other aspect of snail development does the polar lobe influence?

    • How do we know this to be true?

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Snail Development

  • How does gastrulation take place in snails?

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Tunicate Development

  • What makes these organisms rather unique?

  • What type of cleavage pattern do they have?

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Tunicate Development

  • In what way does the pigmentation in Styela partita provide developmental information?

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Tunicate Development

  • What evidence is there of autonomous specification in tunicate blastomeres?

    • transplant experiments

    • RNA hybridization experiments

    • altering β-catenin levels in cells

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Tunicate Development

  • What evidence is there for conditional specifiction?

    • BMP signal from endoderm induces anterior cell to become notocord

      • works through activation of Brachury gene

    • FGF signal induces posterior cell to become mesenchyme

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Tunicate Development

  • When are the embryonic axes established?

    • dorsal-ventral – prior to first cleavage

    • anterior-posterior – prior to first cleavage

    • left-right – first cleavage

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Tunicate Development

  • What is gastrulation like in these organisms?

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Caenorhabditis elegans

  • What does C. elegans look like?

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C. elegans

  • What pattern of cleavage in seen in this nematode?

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C. elegans

  • What determines anterior-posterior axis?

  • What is the importance of the P-granules?

C elegans41 l.jpg
C. elegans

  • When is dorsal-ventral and left-right axes established?

C elegans42 l.jpg
C. elegans

  • In what way is autonomous specification demonstrated in this organism?

    • P1 develops without presence of AB cell

  • In what way is conditional specification demonstrated?

    • AB cell requires cell-cell interactions

    • EMS requires signal from P2

C elegans43 l.jpg
C. elegans

  • cell-cell signaling

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C. elegans

  • Where in this organism is autonomous and conditional specification integrated?

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C. elegans

  • When does gastrulation begin in this organism?