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slides3/21/12
BIO361Exam3
| Question | Answer |
|---|---|
| What tissue from an early gastrula is transplanted into another early gastrula in the region that normally becomes the ventral epidermis? | The Dorsal Lip |
| The donor tissue invaginates and forms a second _______and then a second _________. | Archenteron then embryonic axis. |
| What embryos were formed in the experiment performed by Spemann and Mangold? | Two conjoined embryos |
| What did the experiment show? | It showed that the dorsal lip of the blastopore, and the notochord that forms from it, constituted an "organizer" that could instruct the formation of new embryonic axes. |
| How did the organizer get its properties? | |
| What is the Nieuwkoop experiment? | If animal caps cells are combined with vegetal cap cells, many of the animal cells generate mesodermal tissue. |
| What is mesoderm induction? | all vegetal cells are able to induce the overlying marginal cells to become mesoderm |
| T or F: Only the dorsal vegetal cells can instruct the overlying dorsal morginal cells to become the organizer. | True |
| What is the organizer induction? | The major candidate for the factor that forms the Nieuwkoop center and that instructs the dorsal marginal cells to become the organizer is B-cantenin. |
| What stabilizes B-cantenin in the dorsal portion of the amphibian egg? | Disheveled proteins |
| B-cantenin is initially inhibited by what in the ventral cells? | GSK-3 |
| Disheveled protein is a suppressor of _____ in the ____pathway, and it is originally found in the vegetal cortex of the unfertilized Xenopus egg. | GSK-3 and Wnt pathway |
| Upon fertilization, Disheveled is translocated along the ___________to the dorsal side of the embryo. | Micro tubular array. |
| On the dorsal side of the embryo, _____should be stable, since _____ in inhibited by Disheveled. | B-Cantenin and GSK-3 |
| In activation of organizer-specific gene expression, B-cantenin combines with what transcription factor? | Tcf3 |
| In activation of organizer-specific gene expression, the B-cantenin/Tcf3 complex binds to what gene that is expressed in the Niuewkoop? | Siamois gene |
| In activation of organizer-specific gene expression, Siamois protain binds to the promoter of what gene and activates its expression? | Goosecoid gene |
| In activation of organizer-specific gene expression, the maximum goosecoid expression occurs when there is synergism between what? | THe siamois protein and a vegetally expressed TGF-B signal. |
| When lithium chloride treatment is used to increase the organizer mesoderm throughout the marginal zone, what happens? | The expression of goosecoid is expanded. |
| When eggs are treated with UV light prior to first cleavage, what happens? | Both dorsal-anterior induction and goosecoid expression are significantly inhibited. |
| Injection of goosecoid message into the ventral region Xenopus embryo causes what to happen? | It cause the ventral area to involute, undergo convergent extension, and form a secondary axis. |
| What can goosecoid injection produce? | twinned embryo |
| What are the five major func. of the organizer tissue? | The ability to become: 1. dorsal mesoderm 2. dorsalize the surrounding mesoderm into lateral mesoderm 3. dorsalize the ectoderm into nueral ectoderm 4. initiate the movements of gastrulation 5. cause the neural plate to become the neural tube |
| What is BMP stand for? | Bone morphogenetic proteins |
| What is the default fate of the ectoderm? | To become neural tissues |
| What do specific signals induce the ectoderm to become? | epidermal tissues |
| What are the agents of the previous induction? | BMPs |
| The organizer tissue acts by secreting molecules that block BMPs allowing the ectoderm to become what? | neural |
| If the mRNA for BMP4 is injected into Xenopus eggs, what happens? | All the mesoderm in the enbryo becomes ventrolateral mesoderm, and no involution occurs at the blastopore. |
| What happens if there is overexpression of a dominant negative BMP4 receptor? | The formation of two dorsal axes |
| What is a soluble protein that is activated by goosecoid nuclear expression? | Nogging |
| What is nogging? | It accomplishes two major func. of the Spemann-Mangold organizer |
| What is one thing nogging does? | Dorsalizes mesoderm cells that would otherwise contribute to the ventral mesoderm. |
| What else does nogging do? | Induces dorsal ectoderm to form neural tissue. |
| Nogging binds to ___ and ___ and inhibits their binding to receptors. | BMP4 and BMP2 |
| How was nogging discovered? | cDNA plasmid from dorsalized gstrulae,RNAs were injected into ventralized embryos and further analized. One of the clones contained the noggin gene. |
| The noggin mRNA is found to be first localized and then expressed in what? | Dorsal blastospore lip region and then expressed in notochord. |
| WHat is the role of the chordin and follistatin? | Like nogging, they both bind directly to BMPs and prevent binding with their receptors |
| As gastrulation begins, chordin is expressed where? | At dorsal blastopore lip |
| In later stages of gastrulation, where is chordin message seen? | IN organizer tissues |
| Noggin, chordin, and follistatin mRNAs are all expressed in what? | The blastopore lip and notochord |
| In the regions of noggin and chordin expression, what is totally prevented from binding and forms organizer tissues? | BMP4 |
| As more and more BMP4 molecules bind to ectodermal cells, it activates what expression of genes? | msxl |
| What does msxl do? | induce the expression of epidermal-specific genes |
| In the mesoderm BMP-4 activates ___and____ genes, which give the mesoderm a ventral phenotype. | Xvent2 and XventI |
| What makes induction of tissues by Spemann organizer different? | 1) it has historical significance field of developmental biology 2)far more extensive and complex 3)continue to induce tissues undergoing morphogensis that forms notochord, even after morphogenetic movements are complete. |
| What happens during organogenesis? | Germ layers interact to form the organ rudiments. |
| In human embryo at 5 wks, the shape of organ is characteristics of what? | mammals and vertebrates |
| Organogenesis in human is essentially completed after how many wks of development? | 6-8 wks |
| During neuralation, what is the first adult organ system to appear during vertebrate development? | The CNS (central nervous system) |
| An embryo in the process of neuralation is called? | Neurula |
| What the the three things neauralation accomplish in higher vertebrates? | It creates: 1) neural tube, giving rise to CNS 2)neural crest, migrates away from dorsal surface of neural tube and give rise to diverse set of cells 3) epidermis to cover neural tube once created |
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