470blastomerespecificationandgastrulation - Introduction to...

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Introduction to blastula structure and gastrulation : What does gastrulation accomplish? -process of generating 3 germ layers/body plan -creates gut -internalize yolky cells -create/construct primary body axis -vertebrates – allow CNS induction What are the primary germ layers ? -ectoderm – outer layer (epidermis, neural tissues) -mesoderm – middle (muscle, vertebral column, kidneys) -endoderm – inner layer (gut, many internal organs) What is a blastocoel ? What are the basic types of cell movements that take place in gastrulating embryos? These include epiboly, involution, invagination , and ingression . Can you think of specific examples of these movements? Note: for each of the examples of gastrulation we discussed in class, be able to state which type(s) of morphogenetic movements are involved. -invagination – indentation of cells -involution – surface cells move into interior via ‘rolling’ movement -ingression – cells (individual) break off and migrate -delamination – cells split off and create new layer -epiboly – surface cells spread to encase embryo (close gaps) -convergent extension – groups of cells retain individual cell dimensions; converge to one layer Blastomere Specification and Gastrulation in C. elegans Step-by-step guide to early development 1. sperm entry point is the future posterior end of the zygote -sperm astral microtubules organize cytoskeleton of zygote polarization of actin-rich cortex -segregation of P granules to posterior 2. anterior and posterior differences arise in cortex of zygote, involving PAR proteins -PAR-3 and PAR-6 in anterior, and PAR-2 in posterior localize to their regions which reinforces differences of each end -PAR proteins promote accumulation of mRNAs and proteins in each end of zygote (ex. MEX-5 in anterior) 3. SKN-1 and PIE-1 proteins accumulate in P1; MEX-5 and other proteins accumulate in AB -MEX proteins – keep SKN-1 and PIE-1 from being translated in anterior cell of two-cell embryo (AB)
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This note was uploaded on 03/27/2012 for the course ZOOLOGY 470 taught by Professor Hardin during the Spring '12 term at University of Wisconsin.

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470blastomerespecificationandgastrulation - Introduction to...

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