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To know for embryo midterm.docx

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University of Waterloo
BIOL 303
Dragana Miskovic

To know for embryo midterm - Do not mix up Primary neurulation (differentiation of neural plate (4 steps)) and neural cells differentiation - Be able to draw amphibian egg (indicate where gastrulation starts, which layers form = extrapolation to other species) - Dorsal blastopore lip (spemann’s organizer) equivalent in birds in hensens node o Whole blastopore lip = primitive streak - Vg1, b-catenin – - Large micromere – b-catenin = mesoderm of sea urchin = wnt signalling pathway - Cell movement –ingression (few cell come out of layer) vs. Delamination (2 layers from 1 so several cells separating) o Ingression – large micromeres o Delamination – bird epiblast - Epiboly = cell movement on outer surface - Involution – spread of cells on the interior - Amphibian gastrulation – 2 simultaneous processes – involution (form mesoderm), epiboly (form ectoderm)*** - Autonomous, conditional, cyncitial specification o Cyncitial – cells without plasma membrane, just nuclei o Autonomous – independent of cell movement since it is not influenced by other cells, however its presence around other cells is important (e.g. sea urchin large micromeres = induce skeletal formation)  Frogs – transplant dorsal blastopore lip  Birds – transplant Hansen’s node o Conditional specification – cells affected by surrounding morphogen gradient, cell movements are important (cell not specified until finished moving) o How is cell fate acquired and is this happning before or after cell movement - Syncitial blastoderm = no cells - Cellularization of blastoderm in drosophila = cells have receptors = tight control - MC questions o Gurken (ligand) – dorsal/ventral polarity in drosophila – gurken determine fate of follicular cells to become dorsal which then influence the embryo to dorsalize  Egg nucleus position gurken mRNA in dorsal, gurken protein only exist in dorsal area to influence follicular cells  Cell has membrane receptor for gurken molecules  Before cellularization o Dorsal – goes to nucleus and act as transcription factor to act on embryonic cells  Occur before and continues with cellularization - Hox genes = homeotic genes - Formation of fertilization envelope – 4 factors – proteases, hyaline, - Bicoid – 3 role – inhibit caudal as a translation factor, enhance hunchback (as transcription factor), - Caudal – transcription factor - Trophoblast – help implant embryo, and form embryonic placenta - Inner cell mass form embryo in 2 steps Make epiblast and hypoblast - Epiblast make embryo and amnion - Hypoblast make yolk sac = extra embryonic endoderm - Extra embryonic germ layers important for final exam - Inner cell mass does not separate but amnion form, 2 embryo will share amnion - K
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