BIOL205_Exam3_key_final

BIOL205_Exam3_key_final - Biology 205 Exam III, April 5,...

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Biology 205 Exam III, April 5, 2010 1) [2 points] Apples (potato, stone fruits also accepted) 2) a) [4 points] i) microtubule cytoskeleton allows cortical cytoplasm to rotate 30º, ii) occurs in the zygote, iii and iv) causes mixing of the cytoplasm, making the cytoplasm contents asymmetric on future ventral and dorsal sides, leading to different cell contents in daughter cells after early cell divisions b) [4 points] i) Apical constriction through the actin cytoskeleton, ii) occurs in bottle cells of dorsal blastopore lip, iii) causes a shape change that promotes cellular invagination and migration, iv) causes tissue invagination c) [4 points] i) filopodia or lamellipodia extend, using the actin cytoskeleton, ii) occurs in endodermal cells, iii) causes cells to crawl inward (toward the center of the embryo), iv) decreases the diameter of the gut tube, forcing it to elongate (convergent extension) 3) a) [2 points] E-cadherin forms adherens junctions to create cell-cell adhesion, so that cells can maintain a sheet/epithelium b) [3 points] Ingressing mesoderm and endoderm cells lose E-cadherin. c) [2 points] Endocytosis (turnover) and turn off the E-cadherin gene d) [5 points] Neural tube cells (ectoderm from the neural plate, above the notochord) lose E- cadherin and will become the central nervous system. Neural crest cells lose E-cadherin and become the peripheral nervous system. e) [4 points] Neural tube cells begin expressing N-cadherin. Neural crest cells do not begin to
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BIOL205_Exam3_key_final - Biology 205 Exam III, April 5,...

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