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163 Cards in this Set
- Front
- Back
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The inner cell mass what develops from it? |
Embryo Proper |
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For mouse cells in what stage of division is the final fate always determined? |
32 cell division stage |
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Stage at which the embryo implants into the uterine wall. |
Blastocyst. |
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What else is important about blastocyst? |
It corresponds in form to blastula stage of other animal embryos. |
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Pumping of fluid by trophectoderm. When does this occur and what is the key term? |
Blastocoel and it occurs after division to get tropehctoderm and inner cell mass. And after this the trophectoderm gives rise to extra embryonic structure such as placenta and you get embryo proper from inner cell mass. After this trophectoderm pumps fluid into interior of blastocyst causing trophectoderm to expand and form blastocoel. |
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Blastomere......what sides lead to what in mouse? What does sperm side give rise to? What about side opposite of sperm entry? |
Sperm entry....the blastomere on this side will divide faster and give rise to ICM and polar trophectoderm. Side opposite of sperm entry gives rise to visceral endoderm and mural trophectoderm. |
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Which cells express Oct-4? Which cells express Cdx-2? Why do Oct 4 and Cdx 2 matter? |
By late morula stage cells are on inside and outside. Inside cells express Oct-4 and outside cells express Cdx-2. |
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What about Oct 4 and Cdx 2 by blastocyst stage? What is the relationship between these two transcription factors? |
In blastocyst stage Oct 4 is primairly in ICM. Cdx-2 is primarily in trophectoderm and required for it. Both these transcription factors will inhibit each other. |
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Cells that are apical and have microvili expressed on their surface. What are they and name another important feature about them? |
These are polar cells. They also have basolateral surfaces and sides. |
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When do you get polar cells? |
During compaction and microvili development. |
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Once you have polarized cells, how do you go from 8 to 32+? |
Two types of division Radial clevage leads to 2 polarized cells Tangential clevage leads to 1 polarized cell and 1 nonpolarized cell |
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..............cells are located internally? and express what? |
Non polarized cells are located internally and express Oct4. |
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What exactly do Hippo and Warts do? |
Encode serine and threonine kinases |
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Describe Hippo and Wart pathway. Make mention of some significant details as well Overall what is purpose of Hippo and Wart pathway? |
Purpose: Link cells on outside and inside into combined pathway If cells are surrounded by other cells that activates Hippo pathway Hippo in non polarized cells phosphorylates Wart. Wart is active and will phosphorylate YAP. If YAP is phosphorylated it cant enter nucleus and will degrade. This means that Tead-4 cannot activate expression of downstream genes. |
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Describe Hippo Wart pathway in polarized cells? |
Hippo wont be active so YAP is unphosphorylated and can enter cell and interact with Tead4 to activate downstream targets such as Cdx-2. and other trophectoderm specific genes. |
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Why exactly is the posterior marginal zone so important? |
Determines the A-P axis |
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Where does fertilization take place for chicks? When does egg shell addition take place? |
Oviduct |
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When does clevage take place for chick? |
Uterus |
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When does gastrulation take place and PMZ appear |
After egg hatches |
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What will determine where primitive streak forms? |
The PMZ |
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What defines A-P axis? |
Primitive Streak |
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Describe what determines PMZ location? |
It is gravity Shell and white egg will rotate while in uterus but the the yolk with blastoderm on top will not . Blastoderm will stay upright despite rotation because of yolk. Gravity has greater pull on yolk than blasatoderm so blastoderm will be tipped up and this is where PMZ will be located. |
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Do primitive streaks end up competing if we graft PMZ in multiple locations? |
Yes the longest one will win out and inhibit the other |
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IF you remove the PMZ in a chick what will happen? |
A PS will end up developing in another part of the remaining marginal zone |
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Where all will Vg cause PS formation? |
Xenopus and chick |
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What will block frizzled receptor? |
Cressent |
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What will bind to arrow co-receptor? |
Drizzle |
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Wnt-8 inhibitors with Vg-1 expression...what happens? |
No primitive streak formation |
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How does endoblast and hypoblast relate to PS formation? |
Hypoblast is extraembryonic tissue Group of cells from deep PMZ called hypoblast will eventually displace hypoblast and get in between it and epiblast It is only once this endoblast displacement happens you will get a primitive streak |
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what are primitive streak marker genes? |
Brachyury and Chordin |
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How does hypoblast inhibit primitive streak? |
Vg1 and Wnt8C usually will lead to the expression of Nodal. Nodal leads to Lefty expression Hypoblast usually secretes Cerebrum to inhibit both of these. |
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If you inject Cerebrum what happens? |
It will inhibit primitive streak. However primitive streak still likely to form in another part of marginal zone |
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Explain what we mean by barrier for the formation of hypoblast? |
Endoblast formation serves as a barrier blocking Cerebrus of the hypoblast so now Notch can be expressed and lead to lefty expression. |
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Lefty 1 and Nodal relationship? |
Lefty 1 will inhibit Nodal so other cells cant also start expressing primtive streaks and why only one primitive streak will win out |
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How do we get cells to differentiate into anything we want? |
Stem cells from inner cell mass of blastocyst embryos. change cell culture conditions in vitro and can differentiate stem cells of these into anything you want. |
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How do we modify cells and get them to be a certain form we want? |
1) Microinjection of mRNA into eggs: misexpress a gene of interest. This is basically misexpressing a gene of interest 2) Homologous recombination: Introduce DNA of interest via electroporation. This is controlled |
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How to tell the mixture of wild type and introduced cells of an animal? |
Chimerism. It's color. |
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How to introduce targeted Embryonic stem cells into a mice? |
3 methods 1) Blastocyst injection or morula injection: key here is you inject for embryo for a day before putting back in foster mom 2) Tetraploid aggregations: Only will give rise to extra embryonic tissue |
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How do you actually misexpress a gene? |
Microexpression of DNA into fertilized eggs 1) Need a promoter to drive expression in a particular domain at a particular time 2) cDNA for the gene you want to express This DNA will be incorporated into the genome randomly. |
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What are the main developmental processes? |
CP went to MCG Cell proliferation(CP) Pattern formation Morphogenesis Cell differentiation Growth |
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How exactly does cleavage work where you get lots of division but dont increase the overall size? |
Modified cell cycle without intervening phases of cell growth. Lots of DNA replication followed by cell division |
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Cells knowing what they should become, how they should become it, and when they should become it |
Pattern formation |
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First step of pattern formation? |
Establishment of body axis and germ layers |
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Tissues from which all embryonic organisms are derived? |
Germ layers |
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What allows germ cells to form into organisms? |
Pattern formation |
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Extensive cell movements and rearrangements where cells outside of embryo move inwards as an example? |
Gastrulation |
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Cells become structurally and functionally different from each other? |
Cell differentiation |
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When does cell go from clevage to actually growing stage? |
Gastrulation |
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How do organisms and tissues grow? |
1) Increase total number of cells 2) Increase size of cells 3) Bring about extracellular deposition such as bone or shell |
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Important example of apoptosis? |
Removal of webbing between digits of a frog. Digits will develop between mesenchymal pad called interdigits. To separate the digits you need apoptosis in the interdigit regions |
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Give examples of pattern formation? |
Germ layers, A/P axis and D/V axis |
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As an embryo develops: what happens how much more complex does it get? |
The cells will lose their ability to differentiate but hte organism itself from so many different cells becomes more complex |
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Cells that can develop into all cells of an organism are called what? |
Totipotent |
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When are cells restricted in development and when are they not? |
At 4 cell stage still totipotent but at 32-64 cell stage you get blastocyst and they are now restricted but not at trophectoderm level. You need to be to gastrulation level to truly get that level of restriction |
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How many cells(how much differentiation) do you need in order to be at blastocyst stage? |
About 32-64 cell stage |
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Stable change to a cell that is dependent on changes in gene expression? |
Determination |
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What do fate maps not tell us about a cell? |
It's developmental potential. IT tells us what cells will normally become |
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Cell can still form many different cell types but not every kind? |
Pluripotency |
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How to test whether a cells fate has been determined? |
Transplant your cell of interest into another position of the embryo. You must label the cell If the cell differentiates into what it would at its normal position its fate has been determined. If it differentiates into cells like its surroundings, that means its fate had not been determined |
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Point of no return for a cell? |
Specification |
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Specification vs determination? The key experiments |
Cells transplanted into ectodermic position within the embryo will develop into according to normal development. This is a determined cell. Cell if isolated and put in a neutral environment away from the embryo will develop according to normal fate is called a specified cell. |
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One group of cell influences development of adjacent group of cells? |
Induction |
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What are inducing signals? |
Proteins |
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How are inducing signals passed between cells? |
1) Secreted diffusable molecules 2) Direct cell interactions 3 )Gap junctions First two have to do with receptor interaction. Last one has to do with cytoplasm exchange |
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How does a cell know where it is? |
Morphogen gradient Furtheraway from gradient, less signal you receive. Cells respond differently to different levels of signal |
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what helps produce a reguarly spaced pattern? |
Lateral inhibition It is one way of making cells different |
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How can we make cells different? |
LAPC Lateral inhibition Assymmetric Cell division Polar body formation Cytoplasmic Localization Change/Differences: Go LA Chicago PGH. All very different areas |
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How can we make cells different? Describe each way |
Lateral inhibition is easy Assymetric cell division: Differences due to unequal division of maternal genes and growth factors Polar body formation: Small cells arising from assymetric division is way cells get rid of the egg of chromosomes and reduce number of chromosomes to get haploid number First polar body at animal pole. Second forms after the fertilization and second meiotic division Cytoplasmic localization: Factors unequally divided in daugther cell |
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Key features to ANY model system |
sex life good munch c--- always. Features to any model. size lifespan genetics manipulations accessibility conservation of mechanisms |
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Restoration of diploid number of chromosomes? |
Fertilization |
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Is it gastrulation or differentiation as a stage of development all organisms go through? |
Gastrulation |
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Stage where all organisms resemble each other? When is it? |
Phylotypic stage. This occurs after gastrulation |
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What are characteristics of any vertebrate going through phylotypic stage? |
1) Head and tail 2) distinct anterior-posterior axis 3) Somites segmented on mesodermal tissue along axial neural tube 4) Heart and eye also start developing HPA TSS HPA This S*** Su**s Phylotic: Phylo for Phimosis |
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Frog Xenopus Larvus advantage and disadvantage What is the solution |
Advantage: Large and sturdy fertilized eggs that are accessible. Easy to maintain Disadvantage: Tetraploid and takes 2 years until sexual maturity Solution is use Xenopus tropicalis which is diploid and 6 months until sexual maturity |
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How do we chart different organisms development? Xenopus, Zebrafish, chick and mouse......list them for each? |
Xenopus: Stages Zebrafish: Hours post fertilization Chick: Stages Mice: Somite and structural features |
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Invagination forming opposite of sperm entry? |
Blastopore |
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What all forms from evagination? |
Lungs, liver and pnacreas. These are evaginations of gut tube |
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What is epiboly and how is it accomplished? |
Epiboly is spreading of sheet of cells. Single layer it is accomplished through change of cell shape. Double layer it is caused through intercalation. |
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Blastomere vs Blastula? |
Blastomere is early set of cells from clevage, after 2 divisions you get 4 animal and 4 vegetal cells called blastomeres. Blastula is after 12 stages of cell division |
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Where does blastocoel form? |
Fluid filled cavity beneath animal pole |
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What breaks initial symmetry of Xenopus(lecture 3) |
Blastopore invagination |
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Where are the germ layers located in blastula stage embryo? |
Future ectoderm in animal region Future mesoderm and endoderm in marginal zone Future endoderm in vegetal pole |
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What cell movement is key for formation of primary axis? |
Gastrulation Convergent Extension CE ie CTE forming neural axis: CTE related to neural |
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What all undergoes convergent extension? |
Marginal zone tissue Neural plate |
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Neurula |
Embryo that begins to form a neural tube |
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Neural plate |
Sheet of ectoderm overlying notochord. Once this folds you will get neural tube |
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Mesoderm of the dorsal midline gives rise to what? |
Notochord |
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Paraxial mesoderm gives rise to what? |
Somites |
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Type of intercalation to increase surface area? |
Radial intercalation |
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Type of intercalation where cell sheet narrows and elongates? |
Medio-lateral intercalation |
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Zebrafish end of lecture 3 what all is important about it? |
Fast development time but long time to reach reproduction Embryo will have outer enveloping layer and deep layer Epiboly covers entire cell. Involution is all over cell unlike with xenopus where it is only at blastopore |
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Are axis already established? |
Maternal factors: RNA and proteins deposited during oogenesis. |
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What controls what maternal factor RNA is deposited in egg? |
Maternal effect gene. Will affect later embryonic development through maternal factors |
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Why are maternal factors important and for which ones are they more important? |
Until genome is activated maternal factors will control zyogtes In frog it wont be activated until 12th stage. In mice it wont be activated until 2nd stage. |
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Which pole is pigmented, has the yolk and has the nucleus? |
Animal pole is pigmented with nucleus vegetal pole is with the yolk |
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When is radial symmetry broken for Xenopus? |
3rd division that is perpendicular to first two, assymmetry of protein and mRNA in vegetal region which is what gets separated |
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Does sperm determine D-V or A-P axis? |
Dorsal-Ventral |
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If sperm determines D-V what side is the sperm entry side? |
Ventral side |
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What is the signaling center that results from rotation? |
Nieuwkoop Center. Important to realize this results from rotation. Influences development of surrounding |
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How does sperm lead to rotation? |
Centrioles of sperm are nucleation centers(minus end) for microtubules. Microtubules grow at positive end to get parallel arrangement |
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Separate 4 cell stage and its dorsal and ventral components what will happen? |
Dorsal side with Nieuwkoop loop will develop fine minus a gut. The ventral side wont develop properly. |
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What cells do we inherit characteristics from? |
Germ cells |
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What are germ cells vs somatic cells |
Germ cells are egg and sperm Somatic cells are cells of body |
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In terms of pronuclei what does fertilization do? |
Fertilization will give us 2 pronuclei which will fuse to give us diploid number. Before fusion both cells were haploid. |
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Mosaic Model: Describe |
Nucleus contains assymetrically distributed determinants divided during clevage. this leads to daugther cells becoming different since unequal division. |
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Ability to develop even when some portions of cell are removed or damaged? What theory and word is this about? |
Regulation of sea urchin experiments. Note this is different than the Roux argument of mosaic. Mosaic and regulation are different |
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All cells in body can be traced to what? |
Egg |
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Cells and tissue interact and influence cells and tissue of neighbors? What is this called? |
Induction |
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What was one way to make a decision on mosaic vs regulative theory? |
Induction. Dorsal lip of blastomere you induct into ventral lip region. The dorsal lip will lead to notochord formation. The opposite ventral side usually will lead to skin. Transplant this dorsal lip and you will get secondary axis, neurulation, neural tube and somite formation. |
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How do we get different genes to be expressed in different cells that all have same genetic makeup? |
Control mRNA that transcribes protein Transcriptional control, post translational control, transport, post transcriptional control Differences in cells are caused by differences in gene expression which is done through transcription factors |
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RNA polymerase to bind to and start transcription |
Promoter |
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What binds to enhancers/DNA to promote or inhibit gene expression? |
Transcription factors |
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How can transcription factors be regulated ? |
Negative and Positive Feedback is a major thing |
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What happens if you block cortical rotation? |
You get a ventralized Xenopus with no dorsal structures. Loss of anterior structures |
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What does LiCl do? |
LiCl will ventralize embryo by blocking GSK-3. |
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How do we establish Nieuwkoop Center? |
We must inhibit signals such as GSK-3 that form the ventralizing structures in the dorsal region. |
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What side is the albumin on? |
Dorsal |
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Junction between area pellucida and area opaqua? |
Marginal zone |
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Role of PMZ in chick? |
Sets up Anterior-Posterior axis through the primitive streak |
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What happens to chick egg as it goes through uterus? |
Egg titled with respect to gravity as it goes through uterus. Blastoderm and yolk wont rotate, only egg white and shell. Dense yolk will keep blastoderm upright. Gravity pulls on yolk more than blastoderm. So blastoderm is tipped up and this is where PMZ will arise. |
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Comparing Nieuwkoop Center to PMZ? |
Implant PMZ in marginal zone but not usually where it is. You will get secondary primitive streak with one streak willing. |
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What by itself will lead to ectopic primitive streak formation? |
Vg but NOT wnt-8 |
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Extraembryonic tissue that will not form the embryo? |
Hypoblast |
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How do we make hypoblast? |
PMZ and epiblast cells |
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Role of endoblast in forming the Primitive streak? |
The endoblast will eventually displace the hypoblast and that is when we will see marking/formation of primitive streak |
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Who do we need an endoblast to form a primitive streak? |
Normally hypoblast expresses Cerebrus which will block the expression of Nodal key for lefty for primitive streak. But endoblast will block the cerebrus allowing Nodal to form the primitive streak |
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Why dont we get primitive streak everywhere then from endoblast? |
The expression of Lefty1 which will inhibit Nodal. |
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How is a mouse egg different from chick? |
1) No polarity 2) No localization of maternal factors 3) No yolk Set up assymetry via inner cell mas and trophectoderm PLYM |
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Blastomere where sperm enters will give rise to what? |
ICM and polar trophectoderm |
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Blastomere opposite of sperm entry site for mice will give rise to what? |
Mural trophectoderm and visceral endoderm |
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Are polarized cells with Oct-4 and innercell mass or Cdx-2? |
Polarized cells are with Cdx-2 and unpolarized are with Oct-4 |
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Where does Hippo/Wart pathway come into play? Why is it relevant? |
It shows us how to relate polar vs non polar cells and how they communicate When cells are surrounding the middle cell you will get Hippo activation which will phosphorylate Wart which means that Wart will be active and phosphorylate YAP. YAP when phospohrylated will not be able to ENTER nucleus and activate TEAD and no transcription factors will be able to be activated such as Cdx-2. |
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For mouse what cells will direct primitive streak? |
Anterior visceral endoderm |
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Why is anterior visceral endoderm so important? |
Will form primitive streak and will express Cereberus and therefore it and Lefty1 will inhibit Nodal expression. This means that only in the posterior endoderm can you get a primitive streak where there will be Nodal. |
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In mouse what lead to extra embryonic endoderm and embryonic endoderm? |
Epiblast leads to embryonic endoderm and polar trophectoderm leads to extra embryonic endoderm. |
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How do we incorporate DNA we want to into a embryonic stem cell? |
Electroporation |
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What do tetraploid aggregations do? |
Inject them into ES and you will get extraembryonic cells |
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Microinjection of DNA into fertilized eggs: what happens and how |
You inject this via a promoter that will drive thi gene expression at a particular time while also adding cDNA of gene you want to add. |
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Transgenic vs Chimeric mice? |
Transgenic mice are those that contain DNA that has been introduced into genome Chimeric mice are those that have at least 2 genetically different embryonic cells, such as blastocyst injections or morula aggregation |
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MIce advantages as model? |
short development time small similarity to humans reverse and forward genetics experimental manipulations allowed for like grafting Only problem is cant continuously observe like with chicks |
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When do mice cells become compcated? When do they become polarized and morula? |
At 8 and 16 cell stages respectively |
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What are the two parts of inner cell mass? |
Primitive endoderm and epiblast. EP: As in epiblast and PE as in primitive endoderm. Very easy to remember! |
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Endoderm where does it fall in blastocyst of mice? |
Between ICM and mural trophectoderm |
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What begins gastrulation in a mouse? |
The primitive streak forming from the epiblast. |
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What will primitive streak in mouse do? |
It will form a) mesoderm of embryonic and extraembryonic mice b) Epiblast cells migrating through the node at the top of the streak will form the gut |
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What happens in turning:? |
Mouse embryo becomes enclosed in amniotic membrane and gut is enclosed |
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So the primitive streak is the source of hte mesoderm? |
Until day 10.5 when the tail bud assumes this role |
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Where do streaks regress? |
In the case of both the chick and the mouse it regresses to posterior side of embryo. |
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How do tell or recognize developmental genes? |
Spontaneous mutations and large scale mutagenesis screens |
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Regulate genetic development? |
Gene screen: forward genetics. detect gene expression genetic manipulation |
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Advantages and disadvantages to using a chick |
eggs are available and embyro can withstand manipulation You can open up fertilized egg to observe embryo can observe development outside of egg chick development similar to mice in ovo electroporation to misexpress certain genes genome has been sequenced only problem is little in way of development for a long time |
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For chicks does clevage sit on yolk? |
Yes the blastoderm will sit on the yolk |
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How does a subgerminal space for? |
Pumping of fluid in area between blastoderm and yolk |
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What exactly does epiblast do for chicks? |
Gives rise to embryo proper and some extraembryonic tissue? |
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What exactly does PMZ do for chicks? |
It is thickened region of epiblast and marks the posterior region of embryo |
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Epiblast cells: which ones give rise to mesoderm, endoderm and ectoderm? |
Those that move through streak into space between epiblast and endoderm are mesoderm. If it displaces the hypoblast it will be the endoderm If it doesnt ingress through streak it will be ectoderm |
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What exactly does hte primitive streak do? |
Defines posterior anterior axis for chicks. It's very appearance is hte sign for gastrulation |
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Near the node what will form? |
Anterior to the node you will have folding of the head leading to ectoderm |
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What happens through Hensens Node regression? |
That's when you get axial and paraxial tissue. Axial is the notochord and paraxial is the blocks mesoderm called somites |
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From hensens node how do you get neural structures? |
From the axial tissue get notochord and folding over this will lead to neural plate and folding of neural plate will lead to neural tube. Anterior of neural tube is head and posterior is CNS. Gut will form on endoderm side |
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how do chicks develop extraembryonic structures? |
Must develop extraembryonic structure and vasculature from embryo to shell of membrane. Allows embryo access to yolk and air and gas exchange through allantosis. |
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Key to the lecture 4/5 Xenopus pathway with GSK-3 |
Usually GSK-3 binds to beta catenin and represses it so it cant enter nucleus and activate transcription factors to activate dorsal gene expression specifically. But if yo uhave GSK-3B or recruit Dishevel then Wnt can bind to Dishevel which can inhibit GSK-3 by recruiting axin and that allows for beta catenin to accumulate in nucleus and activate dorsal gene expression |
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For Xenopus what determines D-V pathway? |
Sperm entry |
