Early Development Selected Invertebrates Cleavage n What characterizes

Early Development Selected Invertebrates

Cleavage n What characterizes this process?

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

Cleavage n What happens to the embryo during the mid-blastula transition? n When does this occur?

Cleavage n What is karyokinesis and cytokinesis and how do they compare?

Cleavage n What influences the pattern of cleavage in a particular organism?

Cleavage

Cleavage

Cleavage n How are cell fates specified during cleavage? – cell-cell interactions – asymmetric distribution of morphogenic determinants

Gastrulation What characterizes gastrulation in organisms? n What kinds of movements occur? n

Axis Formation n What are three major body axes?

Sea Urchin Development n What does the cleavage pattern look like?

Sea Urchin Development n What characterizes the blastula stage?

Sea Urchin Development n At what stage are the fates of individual cells determined?

Sea Urchin Development n What role does βcatenin play in specification?

Sea Urchin Development

Sea Urchin Development n 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

Sea Urchin Development n How does gastrulation begin?

Sea Urchin Development n What appears to be responsible for the ingression of primary mesenchyme?

Sea Urchin Development n What appears to be responsible for the initial invagination that occurs during gastrulation?

Sea Urchin Development What is the fate of these vegetal plate cells?

Sea Urchin Development n What happens during later stages of invagination?

Sea Urchin Development

Snail Development n What kind of cleavage pattern characterizes these animals?

Snail Development n Orientation of cleavage plane determines right or left coiling snails

Snail Development n What appears to be responsible for the mosaic development seen in molluscs?

Snail Development n What is the polar lobe and why is it important?

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

Snail Development n What other aspect of snail development does the polar lobe influence? – How do we know this to be true?

Snail Development n How does gastrulation take place in snails?

Tunicate Development What makes these organisms rather unique? n What type of cleavage pattern do they have? n

Tunicate Development n In what way does the pigmentation in Styela partita provide developmental information?

Tunicate Development n What evidence is there of autonomous specification in tunicate blastomeres? – transplant experiments – RNA hybridization experiments – altering β-catenin levels in cells

Tunicate Development n 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

Tunicate Development n When are the embryonic axes established? – dorsal-ventral – prior to first cleavage – anterior-posterior – prior to first cleavage – left-right – first cleavage

Tunicate Development n What is gastrulation like in these organisms?

Caenorhabditis elegans n What does C. elegans look like?

C. elegans n What pattern of cleavage in seen in this nematode?

C. elegans

C. elegans n What determines anterior-posterior axis? n What is the importance of the Pgranules?

C. elegans n When is dorsal-ventral and left-right axes established?

C. elegans n In what way is autonomous specification demonstrated in this organism? – P 1 develops without presence of AB cell n In what way is conditional specification demonstrated? – AB cell requires cell-cell interactions – EMS requires signal from P 2

C. elegans n cell-cell signaling

C. elegans n Where in this organism is autonomous and conditional specification integrated?

C. elegans n When does gastrulation begin in this organism?