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153 Cards in this Set
- Front
- Back
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What are the 6 steps in development?
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gametogenesis, fertilization, cleavage, gastrulation, organogenesis, (optional larval state),
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How many germ layers do diploblasts have and what is their symmetry?
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Diploblasts have two germ layers and are radially symmetrical.
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How many germ layers do triploblasts have and what is their symmetry?
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Triploblasts have three germ layers and are bilaterally symmetrical.
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Where are germ cells derived?
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Germ cells are not derived from any of the three germ layers.
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What are the three types of evidence?
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Correlative (Find It), Gain-of-Function (Move It), Loss-of-Function (Lose It)
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What kind of evidence would be considered correlative?
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If a gene is expressed at the time and location at which it is hypothesized to function
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What kind of evidence would be considered gain-of-function?
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The introduction of the protein produced by the gene in question will cause the function in question.
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What kind of evidence would be considered loss-of-function?
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The expression of a gene is blocked with an antibody and the function that is being examined stops occurring.
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Define homologous structures.
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Homologous structures come from a common originator/ancestor (wing of a bat and human forelimb)
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Define analogous structures.
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Analogous structures have the same function, but evolved separately.
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Who used fruit flies to determine that genes are carried on chromosomes and are the basis of heredity?
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Thomas Hunt Morgan
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List benefits of using drosophila melanogaster.
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Short life cycle, ease of genetic experimentation, external development
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List benefits of using C. elegans.
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Short life cycle, specific number of cells, transparent, ease of genetic experimentation
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List benefits of Xenopus laevis and tropicalis.
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Large eggs, quick development, easy dissection
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List disadvantages of Xenopus laevis and tropicalis.
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Laevis is tetraploid and takes 4 years to develop.
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List advantages of Gallus gallus.
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Large eggs, gene introduction with electroporation or retrovirus
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List disadvantages of Gallus gallus.
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Huge genome, 100s of chromosomes
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What is the unique structure found in Gallus gallus that provides for gas exchange.
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The allantois
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List advantages of Mus musculus.
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Mammalian, sequenced genome, easy genetics
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List disadvantages of Mus musculus.
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Expensive, Develop within mother
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List advantages of brachydanio rerio.
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Fast development, cheaper than mice, sequenced genome
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List advantages of arabidopsis thaliana
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Small fully sequenced genome, short generation time
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Define cell fate.
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Cell fate is the normal developmental pathway by which a group of cells will proceed during embryogenesis to an end-point tissue.
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Define potency.
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Potency refers to the various types of cells that a cell can develop into. Potency depends on where in the cell fate pathway a cell is.
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Define pluripotent.
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Can become many different cell types. Cells in the blastula are pluripotent.
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Define totipotent.
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Can become all cell types. A fertilized egg is totipotent.
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Define induction.
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Induction is the process by which cells signal to surrounding cells to become a specific tissue.
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Define specification.
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Specification is the point in cellular differentiation at which a cell will autonomously develop into a specific cell type even when isolated from surrounding tissue.
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Define determination.
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Determination is the point in cellular differentiation at which a cell will develop autonomously even if transplanted into another cell type.
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Define differentiation.
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Irreversible commitment to one cell type marked by the exit from the cell cycle at G1.
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Define competency.
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The ability of a group of cells to respond to an inducing signal. Related to the developmental stage of an embryo.
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Define autonomous specification.
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Autonomous specification or mosaic development means that a cell becomes progressively committed and does is "autonomous".
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What experiment demonstrates autonomous specification (mosaic development) and how does it do so?
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Roux's frog experiment shows that by destroying one of the two cells at the two cell stage, half of the embryo will die showing that the remaining embryo produces the same cells that it would have if the other cell hadn't been destroyed initially.
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What experiment demonstrates conditional specification (regulative development) and how does it do so?
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Driesch's sea urchin experiment separated the embryo cells at the 2-cell, 4-cell, and 8-cell stages. When separated, the cells each became a fully formed organism showing that the cells adapt to the absence of adjacent cells and automatically take on their role.
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When is induction successful?
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Induction is only successful if the signals produced by the inducer can be received by the responder. This requires the responder to have receptors on the cell surface that can bind with the inducer's signal.
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What are the four methods of cell signaling?
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Diffusion, direct contact, gap junctions.
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What are the three mechanisms of induction signaling?
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Juxtacrine signaling (direct contact), paracrine factors (inducer diffuses from one cell to another), paracrine signal (matrix of one cell induces change in another cell).
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What is an example of juxtacrine signaling and how does it function?
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Notch-Delta. When Notch and Delta transmembrane proteins come into contact, Notch undergoes a conformational change allowing a protease to remove it's cytoplasmic domain. The cleaved portion binds to a transcription factor which then activates the target gene.
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List the six locations that protein synthesis can be controlled.
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Transcriptional control, RNA processing control, RNA transport control, translation control, protein activity control.
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What are the six steps in fertilization?
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Sperm finds the egg, sperm binds to egg jelly (zona pellucida in mammals), enzymes released from acrosome break down jelly, sperm binds to the egg cell membrane, fast and slow polyspermy blocks, sperm and egg nuclei fuse.
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What are some examples of species specific recognition methods?
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bindin on the tip of sperm will only bind to eggs with the correct receptors (ie the same species), glycans on ZP protein in the zona pellucida also ensure species specificity.
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What hormone stimulates the release of the egg in humans?
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luteinizing hormone
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What are some differences between sea urchin fertilization and mammalian fertilization?
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Sea urchin fertilization occurs externally, mammals have a zona pellucida layer instead of the egg jelly layer,
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What are the steps in the Wnt pathway?
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Wnt-Frizzled-Disheveled-GSK 3-B catenin-transcription
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What are the steps in the TGF B Superfamily pathway?
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TGF B Ligand-Receptor II-Receptor I-Smad Activated-Smad dimerization-transcription
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What are the steps in the RTK pathway?
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RAS-RAF-MAP Kinase Cascade-Transcription Factor-transcription
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Where are steroid receptors located and why?
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Receptors are located intracellularly. Since hormones are small and hydrophobic, they can pass through the plasma membrane.
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Describe the fast block for polyspermy.
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The fast block prevents more sperm from attaching to the cell membrane. An Na+ influx shifts the membrane potential from negative to positive preventing more sperm from binding. This occurs within 1-3 seconds and last for approximately a minute.
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Describe the slow block for polyspermy.
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Cortical granules near the surface of the egg's surface (sea urchin) release an enzyme that clips off the egg's binding receptor and thus any sperm bound to them. This occurs 15-60 seconds after sperm binding and is permanent. It also permanently alters the vitelline envelope, creating the fertilization envelope. The slow block is initiated by an increase in calcium.
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What does the increased pH caused by sperm binding initiate in the cell and after how long?
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DNA replication commences 20-40 minutes after pH increase and protein synthesis increases 5-10 minutes after pH increase.
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What are the layers to the mammalian egg?
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Cumulus layer, zona pellucida, and cell membrane
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What proteins on the sperm tethers it to the zona pellucida?
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SED1 and GalT
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What protein in the egg cell does SED1 bind to?
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SED1 binds to ZP2/ZP3
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What protein in the sperm cell does GalT bind to?
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GalT binds to glycans on ZP3
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What is the goal of cleavage?
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The goal of cleavage is to rapidly increase the number of cells in the embryo.
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How is the cell cycle different during cleavage than during regular cell growth?
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Cells in cleavage do not go through the G1 and G2 phase, but constantly alter between the S and M phase.
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What controls the pattern of cleavage?
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The amount of yolk and its distribution determines the cleavage pattern of an embryo.
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What is the cleavage pattern of sea urchins?
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They have radial cleavage.
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What is the cleavage pattern in mollusks?
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Sea mollusks have spiral cleavage.
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What is the cleavage pattern in mammals?
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Mammals have asynchronous rotational cleavage.
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What is the cleavage pattern in Xenopus?
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Xenopus has holoblastic cleavage.
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What is the cleavage pattern in birds and fish?
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Birds and fish both have discoidal cleavage (disc on top of yolk)
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What are the effects of dense yolk?
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Dense yolk slows cell division .
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In order for a mollusk to be left coiling, what must be the case?
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The mother's genotype must by d/d (she can be right coiling, but all offspring will be left coiling).
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What occurs at the mid-blastula transition?
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The embryo's cells enter a traditional cell cycle, the embryo begins transcribing it's own RNA, and gastrulation begins.
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What is gastrulation and why does it occur?
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Gastrulation is the movement of cells to a different location in the embryo where they can receive the proper signals to become differentiated. Another goal of gastrulation is the formation of the three germ layers. The final goal of gastrulation is the formation of the main body axes .
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What is the end product of cleavage?
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After cleavage occurs, a blastula is produced with a central cavity called a blastocoel.
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What cellular action allows for the creation of the epithelial tube?
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Contraction of the actin belt within the sheet of epithelial cells causes invagination and eventually the pinching off of the epithelial tube.
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What is invagination?
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The infolding of a region of cells.
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What is involution?
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The inturning of an expanding outer layer of cells to ride along the interior of the layer.
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What is ingression?
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The migration of individual cells from the surface to the interior. This action creates the mesenchymal cells from epithelial cells.
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What is epiboly?
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The movement of sheets of epithelial cells to cover the embryo.
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What is convergent extension?
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The lengthening of a group of cells in the long axis while shortening in the perpendicular axis.
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What is the first step in sea urchin gastrulation?
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Cells ingress to become the primary mesenchyme.
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What causes cells to ingress?
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Changes in cell-cell and cell-matrix adhesion push the cells into the blastocoel.
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What is the second step in sea urchin gastrulation?
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Mesenchyme cells migrate along the walls of the blastocoel and attach to the extracellular matrix.
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How do primary mesenchyme cells attach to the ECM.
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Primary mesenchyme cells use filipodia to attach to the ECM, they also are used to detect chemical cues.
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What is the third step in sea urchin gastrulation?
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Cells are pushed inward toward the center of the blastula. This is called invagination.
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What causes the cells to push inward during invagination?
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Secretory vesicles near the exterior cell membrane release a compound called Condroitin sulfate proteoglycan into the inner lamina where it absorbs water and swells, pushing the cells inward.
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What is the fourth step in sea urchin gastrulation?
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Convergent extension converts the dome formed by invagination into a tube.
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What is the archenteron and where is it found in sea urchins?
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The archenteron is the primitive gut and it is found in the invaginated space.
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What causes the edge of the archenteron to move in sea urchins?
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The archenteron is pulled toward the animal pole by filipodia.
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In frog fertilization, where does the sperm enter?
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The sperm always enters at the animal hemisphere which will eventually become the ventral side.
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What occurs upon sperm entry in the frog?
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The cortex rotates approximately 30 degrees relative to the inner cytoplasm.
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Where does gastrulation begin in the frog and what is the structure called where it occurs?
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After the cortex has rotated, approximately 180 degrees from the point of sperm entry at the dorsal blastopore lip.
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What is the first step in frog gastrulation?
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Constriction of bottle cells induces blastopore invagination.
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What is the second step in frog gastrulation?
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The marginal zone cells (cells at the intersection of the animal and vegetal pole) through the blastopore.
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What is the third step in frog gastrulation?
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The ectoderm expands to cover the outside of the embryo.
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What is the fourth step in frog gastrulation?
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Convergent extension moves mesoderm around wall of the blastocoel
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What happens to the blastocoel?
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The blastocoel disappers and is replaced by the archenteron.
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What does the ectoderm produce?
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The ectoderm produces skin and the central nervous system.
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What does the mesoderm produce?
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The mesoderm produces muscles, connective tissue, blood, and blood vessels. (Also produces the notochord, bones and cartilage, circulatory and urogenital systems in vertebrates.)
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What does the endoderm produce?
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The endoderm produces the entire digestive system, liver, lungs, pancreas, and salivary glands.
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What is Hensen's node?
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Hensen's node is found in the chick embryo and is functionally equivalent to the frog dorsal blastopore lip.
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What is the Primative Groove?
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The Primative Groove is found in the chick embryo and is functionally equivalent to the frog blastopore.
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What is compaction and when does it occur?
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Compaction occurs in mammals at the 8-cell stage. It is basically the formation of compact ball of cells.
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What happens to a human embryo when it enters the uterus?
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The embryo hatches out of the zona pellucida, allowing surface proteins in the trophectoderm to attach to the extracellular matrix of the uterus.
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When does implantation occurs in humans?
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Implantation occurs immediately after the blastula stage in humans.
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What is the most common type of twins in humans?
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Separation of the inner cell mass causes the formation of two amnions but only one chorion.
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When does gastrulation occur in humans?
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Gastrulation begins immediately after the embryo is implanted and the placental connection to the mother is formed.
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What is the goal of neuralation?
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The goal of neuralation is to separate the ectoderm into neural and epidermal cell fates.
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What type of cadherin binds the epidermis together after the formation of the nerual tube?
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E-cadherin
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What type of cadherin is found in the neural tube?
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N-cadherin
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How can cadherin funciton be regulated?
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Transcription and endocytosis
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What structure is made up of cells cells bound the notochord
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The medial neural hinge point cells anchor to the notochord.
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What cells hinge at the junction of the forming neural tube and the epidermis
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dorsolateral hinge point cells
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What are the four regions that neural crest cells migrate to?
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Cranial region, trunk region, vagal and sacral region, and the cardiac region
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What are the three types of cells that are created by neuralation?
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epidermis, neural crest cells, and neural tube cells
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What does the intermediate mesoderm form?
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Forms the uro-genital system.
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What does the paraxial mesoderm form?
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Forms the head and somites.
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What does the lateral plate mesoderm?
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Forms the circulatory system.
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What vitamin helps prevent neural tube defects?
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Folic acid.
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Where is the Speeman's Organizer located?
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The Speeman's Organizer is located in the Dorsal Blastopore Lip.
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What structures do integrins connect?
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Integrin connects the extracellular matrix and the actin cytoskeleton.
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What is needed to induce mesoderm formation in the animal cap?
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A signal from the vegetal pole.
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What cells in a embryo form the mesoderm?
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The equitorial cells.
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What type of mesoderm do dorsal equitorial cells form?
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Notochord, muscle, and neural tube
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What type of mesoderm is produced by ventral equitorial cells?
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Mesenchyme, epidermis, blood
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What determines dorsal/ventral orientation?
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Different signals from the two sides of the vegetal pole.
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What tpe of cells are formed when the dorsal vegetal pole and the animal cap are combined?
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Notochord, somites, and organizer
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What tpe of cells are formed when the intermediate vegetal pole and the animal cap are combined?
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Muscle, Kidney
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What tpe of cells are formed when the ventral vegetal pole and the animal cap are combined?
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Mesenchyme, blood
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Give the pathway by which the organizer is induced.
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Nieuwkoop center signals the formation of the organizer with dorsal mesoderm inducing signals.
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What are the general inducers of mesoderm fate in Xenopus?
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Xnrs (Xenopus nodal-related)
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What are the two roles of B-catenin?
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B-catenin anchors cadherins to actin and serves as a transcription factor in the Wnt pathway.
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Where is the concentration of B-catenin high?
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B-catenin is found in high concentrations on the dorsal side of an embryo.
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What two proteins interact to activate the transcription of Xnrs?
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VegT/Vg1 and B-catenin
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What structure is formed when VegT/Vg1 is high and Xnr is low?
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Ventral mesoderm is formed.
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What does the organizer give rise to?
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The notochord and the neural crest.
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List the proteins that induce head formation.
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Dickkopf, Frzb, Cerberus
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List the proteins that induce neural and dorsal mesoderm formation.
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Chordin, Noggin, Follistatin
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List the proteins that induce neural tube patterning?
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sonic hedgehog
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What does Wnt inhibit?
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Head formation
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What does BMP inhibit?
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neural and dorsal mesoderm formation
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The presence of TGF-B induces the formation of what kind of neurons?
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dorsal neurons
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The presence of sonic hedgehog induces the formation of what kind of neurons?
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ventral neurons
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What two compounds regulate somitogenesis?
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FGF and retinoic acid
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How are unneccessary genes silenced?
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DNA methylation
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What organisms do not methylate DNA?
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flies and worms
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What compound can reduce DNA methylation?
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5-azacytidine
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How does imprinting occur?
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A chromosome from one parent is methylate and the chromosome from the other is not
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What is the primary conflict between the mother and fetus?
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The mother wants to remain healthy enough to have large families and the fetus wants to take as many nutrients as possible.
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What is the function of an acetyl group.
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Reduces the affinity of DNA for histones, facilitating DNA transcription
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What is the function of histone methylation.
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Inhibits acetylation.
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What type of RNA inactivates X chromosomes in humans and mice?
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Xist
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What is the goal of myogenesis?
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specification and differentiation of muscle cells.
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What protein induces muscle cell formation?
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myoD
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What two genes work together to regulate muscle cell fate?
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myoD and myf5
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What is unique about the expression of myoD and myf5?
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They activate their own transcription.
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What are the steps of gastrulation in sea urchins?
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Ingression, migration, invagination, convergent extension
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What are the steps of gastrulation in the frog?
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Invagination, involution, epiboly, convergent extension, migration
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What are the steps of gastrulation in chick?
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Ingression, migration
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What are the steps of gastrulation in humans?
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ingress, migrate
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