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157 Cards in this Set
- Front
- Back
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T/F. The fusion of genetic material is essential for the early steps of development.
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F
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How many cells make up a sperm?
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1
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Which organelle is present in large numbers in sperm and why?
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mitochondria; for energy
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T/F. Sperm have a reduced amount of cytoplasm.
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T
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Which is more important for early development, the sperm nucleus or the acrosomal vesicle?
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acrosomal vesicle
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Compare a sea urchin egg to a mammalian egg.
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sea urchins have jelly and vitelline layers whereas mammals have cumulus and the zona pellucida. Mammals have a corona radiata. Both have a large volume of cytoplasm, lots of nutrients, cortical vesicles and mitochondria.
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Which part of the egg is more important during early development, the cytoplasm or the nucleus?
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cytoplasm
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T/F. The jelly layer is acellular whereas the cumulus is composed of cells.
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T
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Where is the egg cortex located? Describe it.
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beneath the plasma membrane; full of microvilli, microfilaments and cortical granules.
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T/F. Most female germ calls are haploid at the time of fertilization.
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F. in many species fertilization occurs before the end of differentiation, before the oocyte becomes a mature egg
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What happens if fertilization happens before or after the ideal phase of meiosis?
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increased risk of polyspermy
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Which changes during egg maturation help prevent polyspermy?
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cytoskeletal changes, electrical properties of plasma membrane, optimization of intracellular Ca release system
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Why is polyspermy detrimental?
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sperm provide a centriole which divides to form the two poles of the mitotic spindle during first cleavage therefore polyspermy results in more than one plane of cleavage
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What are the 5 steps involving interaction between egg and sperm?
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1- chemoattraction and sperm activation; 2 - acrosomal reaction; 3- binding of sperm to extracellular envelope; 4; passage through extracellular envelope; 5- fusion of egg and sperm cell membranes
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What triggers the acrosomal reaction in sea urchins? In mammals?
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the jelly; binding to the zona pellucida
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T/F. In sea urchins, binding happens to the vitelline envelope happens before the acrosomal reaction
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F
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T/F. The acrosomal reaction results in the release of vesicle contents which help digest the jelly and cumulus layers.
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F. jelly and zona pellucida
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Why are sperm inactive in the tesis?
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high CO2 results in low pH therefore dynein is inactive
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What provides directionality to sea urchin sperm? How?
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chemotactic peptides (resact) released from the jelly; results in increase in cGMP causing a Ca influx, increasing mitochondrial ATP and further activating dynein ATPase
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What happens once a sea urchin sperm contacts the egg jelly?
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initiates acrosome reaction, exocytosis of acrosomal vesical, proteases and proteasomes that digest the jelly, acrosomal process adheres to the vitelline envelope and digests it
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T/F. The acrosome reaction is species-specific.
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T
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What mediates the recognition of the egg surface by the sperm?
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bindin
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T/F. Bindin is highly conserved.
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F. species-specific
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T/F. The acrosome reaction is a calcium-dependent process.
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T
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What allows for the extension of the acrosomal process?
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polymerization of globular actin
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What does the calcium influx during the acrosomal reaction lead to?
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activation of Na/H pump, increase in pH, phospholipase activation leading to an increase in IP3 leading to the release of internal Ca stores
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T/F. When bindin particles and eggs are from the same species, agglutination occurs.
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T
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Why is the entire surface of an egg not bound by sperm?
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receptors for bindin are limiting
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At which 4 levels are species-specific interactions seen?
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attraction, activation, acrosome reaction, binding to vitelline membrane
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Which part of the mammalian egg functions most similarly to the sea urchin jelly? What do they have in common?
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zona pellucida; bind sperm and initiate acrosomal reaction
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What is the role of ZP3 and where is it found?
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crosslinks sperm receptors and causes calcium influx leading to exocytosis; zona pellucida/jelly
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What leads to the formation of the fertilization cone in sea urchins? What is it analagous to?
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fusion of sperm and egg causes the polymerization of actin; the sperm's acrosomal process
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What are the 2 main mechanisms to prevent polyspermy?
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fast block and slow block
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Describe the fast block.
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increase in membrane potential caused by Na influx, sperm cannot fuse with membranes that have a positive resting potential
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T/F. Resting membrane potential of the egg is maintained actively.
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T
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T/F. Polyspermy rates are higher in saltier water.
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F.
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Describe the slow block.
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exocytosis of cortical granule content in the extracellular space contained by the vitelline envelope, granule contents bind to the vitelline envelope to form a fertilization envelope which moves away from the egg
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T/F. The slow block is transient.
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F. fast block is transient
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Which block clips off any sperm attached to bindin receptors?
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slow block
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How is the egg cell membrane cleaved from the vitelline envelope?
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CGSP released from cortical granules cleaves linker proteins
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What is the role of mucopolysaccharides and what releases them?
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form an osmotic gradient causing water to enter and swell the space between the vitelline envelope and the cell membrane; cortical granules
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What is responsible for the hardening of the fertilization envelope?
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peroxidases and transglutaminases released from the cortical granules
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T/F. The egg cell membrane becomes the fertilization envelope.
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F. vitelline becomes it
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What is the role of the hyaline layer?
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provides blastomere support during cleavage
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What causes the masive exocytosis of cortical granules?
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increase in intracellular Ca (Ca wave)
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Which organelle releases Ca for the Ca wave? What do the Ca release channels depend on?
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ER; Ca
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T/F. The calcium wave cannot occur on the absence of Ca.
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F. It is delayed when phospholipase C is inhibited
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T/F. Phospholipase/IP3 is essential for the calcium wave.
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F.
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How is PLC activated?
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by a TK which is activatedd by soluble factors from sperm or bindin binding to the spermm receptor
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T/F. TS resumes within minutes after sperm entry.
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F. not til later, protein synthesis does though
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T/F. Sperm entry leads to activation of DNA and protein synthesis.
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T
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T/F. The number of cells increases drastically during gastrulation.
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F. during cleavage, tapers off during gastrulation
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Which cell cycle stages do blastomeres go through?
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M and S
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When do cell divisions stop being synchronous?
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after the MBT
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Which stages are added after the MBT?
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G1 and G2
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T/F. Yolk distribution determines the plane of cleavage.
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F. not always but it constrains it
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T/F. The first 3 sea urchin divisions are meridional.
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F. First two are but the third is equatorial.
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What happens during the fourth cleavage in sea urchins?
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animal half undergoes one meridional cleavage, vegetal undergoes unequal equatorial (macro and micromers)
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What are the 3 germ layers?
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ectoderm, endoderm, mesoderm
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T/F. Animal cells become the endoderm.
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F. vegetal become endo, animal become ecto
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How can specific cell fates be acquired during cleavage?
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asymmetric distribution of determinants; cell interactions
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What happens when the vegetal hemisphere of a blastoderm is removed?
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abnormal larva, complete animalization, only ectoderm
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What happens when the animal cap and micromeres are present but the rest of the blastoderm is not?
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recognizable larva, endoderm forms from animal layers instead of vegetal layers
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T/F. Micromeres are conditionally specified.
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F
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What happens when additional micromeres are transplanted to the animal cap of a 16-cell embryo?
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micromeres induce endomesoderm gene expression from animal pole cells, secondary primitive gut forms
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Commitment to a certain fate can be divided into which two stages?
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labile (specification) and irreversible (determination)
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T/F. The process that leads to specific cell fate occurs in stages at different times during development.
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T. it is progressive
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What is gastrulation?
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invagination of blastomeres which will give rise to internal organs and mesoderm; to make a 3D organism
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Which side becomes flatter during early gastrulation?
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vegetal side (vegetal plate)
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Which forms first, the anus or the mouth?
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anus
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What do micromeres become after ingressing into the blastocil?
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primary mesenchyme cells
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What is the role of the secondary mesenchymal cells during gatrulation?
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help pull the invaginating endoderm to the other side (towrad the animal ectoderm) where the mouth will be formed
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T/F. The mouth is the site of the original blastopore.
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F. anus
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What is the role of the skeletogenic mesenchyme cells during gastrulation?
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extend filopodia then fuse within the prospective ventrolateral region of the blastocoel and form spicules of the larval skeletal rodes
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What provides the motive force for invagination?
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apical contraction of vegetal plat cells, vesicles release CSPG (chondroitin sulfate proteoglycan) into hyaline layer which absorbs water causing swelling
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What is the archenteron?
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the primitive gut
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What is the first phase of archenteron invagination?
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changes in cell shape and composition of the hyaline layer
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What is the second phase of archenteron invagination?
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convergent extension
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T/F. During convergent extension, the blastopore becomes wider.
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F. narrower
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T/F. Cell division does not occur during convergent extension.
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T
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What is the third phase of archenteron invagination?
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secondary mesenchyme cells provide mechanical force (by extending filopodia) and spacial coordinates for proper fusion of the archenteron to form the mouth
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Towards which part of the embryo do the filopodia extend and how do they sense direction?
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lateral side of animal pole; respond to chemoattractants
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T/F. Micromeres have lots of beta catenin.
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T
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T/F. LiCl results in a decrease in beta catenin.
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F. increase
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What is the role of GSK3 beta?
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phosphorylates beta catenin, allowing it to be targeted for degradation
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What happens to micromeres when beta catenin is down regulated? overexpressed?
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few express beta catenin, development stops; other layers accumulate beta catenin, embryo is abnormal with a massive gut
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T/F. LiCl inhibits GSK3.
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T
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Wnt binds to ___ which activates/deactivates disheveled.
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frizzled; activates
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T/F. Active disheveled activates GSK3.
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F. deactivates
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T/F. When GSK3 is active it precents the dissociation of beta catenin from the APC protein.
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T
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T/F. Beta catenin becomes a TF when GSK3 is active.
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F. inactive
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T/F. The canonical Wnt pathway is controlled by a double negative mechanism.
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T
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Which TFs does beta catenin interact with to allow TS?
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LEF/TCF
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What happens when beta cat or APC are mutated?
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unstable complex, beta cat not targeted for degradation, allows beta cat to go to the nucleus and activate TS, cancer cell
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Where is disheveled localized before fertilization? Which cells in this region can quickly experience wnt pathway activation?
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at the vegetal pole; micromeres
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What are the 2 main functions of micromeres?
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expression of endomesodermal signals; expression of gene that confer a skeletogenic fate
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Beta catenin and ____ activate ___ which represses _____. This occurs in _____.
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Otx; Pmar1; HesC; the micromeres
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Describe the cleavage in amphibians in 3 words.
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unequal, radial, holoblastic
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T/F. In amphibians, cells on the animal side are bigger than those on the vegetal side.
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F. vegetal bigger than animal
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What do the animal cap, marginal and vegetal cells give rise to?
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ecto, meso, endo
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What happens when the animal cap is put in direct contact with the vegetal cells?
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animal cap cells become meso instead of endo
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T/F. The yolk is concentrated in the vegetal cap.
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T
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On which side does the frog head form?
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anterior
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What determines dorsal and ventral?
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sperm entry.... dorsal is opposite the site of sperm entry
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T/F. The specification map has broader areas of division compared to the fate map.
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T
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On which side does the blastopore lip form?
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dorsal
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What is the role of bottle cells?
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source of force for invagination, move inward to form blastopore lip
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Which cells have been internalized by the end of frog gastrulation?
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endoderm
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What begins to form during mid-gastrulation in frogs?
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archenteron
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What happens in frogs if you take dorsal cells and graft them to the ventral side of another embryo?
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2nd site of gastrulation forms, 2 notochords, 2 neural tubes
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What is determined in the early frog gastrula?
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only the dorsal lip of the blastopore
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What happens when eggs are centrifuged after cortical rotation took place? What was the conclusion of this experiment?
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cytoplasm moved towards site of sperm entry, second axis formed, double headed embryos; something in the cytoplasm leads to formation of second axis
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T/F. The grey crescent encompasses the sperm point of entry.
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F. it is opposite of it
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What forms at the grey cresecent?
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dorsal lip
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Which part of the frog embryo is pigmented?
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animal region
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What happens if an embryo is divided in the middle of the grey crescent? If only one part receives the crescent?
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2 normal structures form; 1 normal structure, 1 belly piece
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T/F. Cytoplasm from vegetal blastomeres is necessary but not sufficient to induce dorsal development.
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F. it is necessary and sufficient
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What happens if you transplant cells near the dorsal lip to the vegetal region of another blastomere? If the second embryo's vegetal pole is irradiated?
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2 axes form, double-headed; normal development
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Which part of the frog embryo/blastomere is considered the organizer?
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dorsal lip of blastopore
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Where is beta catenin predominantly located at the 2 cell stage?
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in nuclei of dorsal cells
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What happens when both blastomeres of a 2-cell from embryo are injected with DN GSK3? Why?
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formation of a second dorsal axis (2-headed); wt GSK3 suppresses dorsal fate
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How does DN GSK3 affect betacatenin?
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blocks GSK3 so beta catenin is active
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What happens to Dsh during cortical rotation? What hppens to Wnt11 mRNA?
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translocates quickly on MTs from vegetal region to dorsa lip and starts to get expressed; slowly transported
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T/F. Dsh needs Wnt11 to function.
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T
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Where is the Wnt pathway activated?
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dorsal side
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T/F. Beta catenin is involved in ventralization.
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F. dorsalization
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T/F. Beta catenin proteins allow for the exxpression of the siamois gene,
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T
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What is the characteristic organizer protein? In which area of the cell is it expressed?
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goosecoid; dorsal
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T/F. The siamois protein is necessary and sufficient for goosecoid gene expression.
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F. it is necessary but TFs and TWIN are also required
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How are the TFs which associate with the siamois and TWIN proteins turned on?
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paracrine signals
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T/F. UV decreases goosecoid expression.
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T
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T/F. LiCl decreases goosecoid expression.
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F. increases
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T/F. Goosecoid is necessary and sufficient to induce a new axis.
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T
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T/F. All vegetal ells can induce overlying marginal cells to become mesoderm.
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T
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T/F. All vegetal cells can instruct marginal cells to become the organizer (able to induce a complete new axs).
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F. only dorsal most vegetal cells
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T/F. Inhibiting cortical rotation prevents the formation of the DV axis.
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T
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How could you rescue inhibition of rotation?
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transplant dorsal cytoplasm
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What happens if a second cortical rotation occurs?
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additional axis
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What is the Nieuwkoop center and how is it formed?
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found in dorsal endoderm, induces the organizer; depends on cytoplasmic rotation
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T/F. Beta catenin mRNA are maternally contributed and ubiquitously expressed.
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T
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T/F. Nodal related is low where beta catenin is expressed.
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F
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What happens if you transplant a young gastrula dorsal lip to another young gastrula? Advanced to young?
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secondary axis, head duplication; duplication of posterior dorsal structures
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T/F. The identity of cells is changing as the move into the blastopore.
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T
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What happens when you take ectoderm from an archenteron and transplant it into an early gastrula?
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anterior or posterior duplications depending on where the piece was taken from
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Why is the polarity of gastrulation important?
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it predicts the AP axis
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What are the functions of the organizer?
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initiate gastrulation, induce dorsalization of surrounding meso and overlying ecto
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T/F. DV establishment follows AP formation.
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F. AP follows DV
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T/F. The first portion to involute will become the most posterior mesoderm.
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F. anterior
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T/F. Epidermis is a default fate.
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F. neural
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What is the function of the organizer in neural ectoderm?
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inhibit it from becoming epidermis
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Where is noggin expressed?
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dorsal marginal, dorsal blastopore lip, developing notyochord
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What effect does noggin have on a UV treated embryo?
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rescues it
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What does BMP induce the formation of?
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epidermis
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T/F. BMP4 has a ventralizing function.
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T
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T/F. Organizer molecules have a ventralizing function.
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F. dorsalizing
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How to paracrine factor antagonists affect the AP polarity?
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help establish it
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What is the main role of secreted organizer molecules?
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inhibit BMP
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