Download BIO380 Summer 2010 TERM TEST 2 Instructor: Yekaterina Poloz Date

BIO380 Summer 2010 TERM TEST 2
Instructor: Yekaterina Poloz
NAME __________________________________
Date: June 16, 2010
ST#__________________________
Lecture section (TOTAL 78 marks).
Multiple choice. Circle the best answer. 1 mark each. (TOTAL 6 marks)
1. Cleavage is a specialized cell division, as compared to somatic cell division, due to:
a) absence of cytokinesis
b) absence of cell growth
c) absence of the spindle apparatus
d) condensation of cellular components
e) none of the above
2. This is the right sequence of events:
a) compaction, morula formation, cavitation, blastocyst formation, hatching
b) morula formation, compaction, blastocyst formation, cavitation, hatching
c) morula formation, compaction, cavitation, blastocyst formation, hatching
d) compaction, morula formation, hatching, cavitation, blastocyst formation
e) morula formation, hatching, compaction, cavitation, blastocyst formation
3. The following molecules are not involved in the morphogen gradient nodal flow model:
a) kinesin
b) dynein
c) Lefty
d) Nodal
e) BMP
4. Monocilia that create the nodal flow are responsible for the special rotating movement because
they are missing:
a) the spokes
b) the central doublet
c) dynein
d) kinesin
e) microtubules
5. Which of the following is not a neurotrophic factor:
a) NGF
b) Neurotrophin
c) Brain-derived growth factor
d) Neuregulin
e) All of the above are neurotrophic factors
6. NCC precursors in the neural plate are signaled by:
a) FGF
b) BMP
c) Notch
d) Wnt
e) all of the above
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NAME _________________________________________
ST#_________________________
Fill-in-the blank. Wright in full. 1 mark each. (TOTAL 8 marks).
1. Another name for E-cadherin is _________uvomorulin____________________
2. Nutrient exchange occurs through ______villi__________ of the chorion
3. First cells that enter through the node become the ___chordamesoderm or notochord____
4. LIM-1 mutant embryos will have no ___head or forebrain_______________________
5. _____neuroepithelial____________ cells are stem cells of the central nervous system
6. __FoxD3 or Slug_________________ is a transcription factor important in NCC formation
7. A chemoreppelent of NCCs is __________semaphorin_________
8. Dermomyotome is part of ________somite or paraxial____ mesoderm
Label the diagram. (TOTAL 5 marks).
Syncytiotrophoblast Epiblast Hypoblast Cytotrophoblast Endometrium or endometrial lining or epithelium 2
Short Answer. Use the space provided. (TOTAL 34 marks).
1. How can a pregnancy results in conjoined twins (1 mark).
If the inner cell mass partially splits into two.
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2. What is N-CAM. List 3 characteristics of N-CAM (4 marks).
N-CAM: Neural Cell Adhesion Molecule (1)
Other 3 marks for any three from below:
N-CAM is a glycoprotein: it contains 30% sialic acid (neuraminic acid) by weight
Originally isolated from neural retina where it functions developmentally
It is a member of the Immunoglobulin Superfamily
It is one of more than 20 CAMs: for example: L-CAM is Liver CAM
Due to splicing, a single N-CAM can produce 100 different forms onf N-CAM
Mediates Ca2+-independent cell adhesion
Lastly they could have also put that NCAM is important for NCC adhesion. NCAM disappears during
NCC adhesion and reappears when they reach their destination. This would be only 1 mark since they
are not really characteristics.
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3. What are the two adhesion molecules involved in the adhesion of the blastocyst to the endometrial
lining. What are their inductive effects that lead to implantation. What would a null mutation in the
embryonic gene for the second adhesion molecule result in and why (10 marks).
Cell Adhesion Molecules & Implantation
Two cell adhesion molecules have been shown to function during embryo implantation: L-selectin and
trophinin.
L-selectin (Lymphocyte selectin) (1) (1/2 mark if L instead of lymphocyte)- involved in initial
adherence (1) it is present on the blastocyst and binds to sugars on endometrial lining (1) -initiates
events leading to trophinin expression by maternal cells (1)
Trophinin (1)
- once trophinin molecules appear on endometrial cells, trophinin-trophinin binding occurs
(homophilic) (1) -strong adhesion event (1)
- trophinin-trophinin binding leads to creation of syncytiotrophoblast due to proliferation of cells of
the cytotrophoblast in contact (1)
A null mutation in trophinin in the mother or the embryo will lead to no implantation due to poor
adhesion and no syncytiotrophoblast creation (1)
These events are summarized in the following graphic (1 mark for nice figure or overall clarity and
language)
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4. What is an example of infectious agent teratogen. What condition does it result in and how is it
characterized (4 marks).
1 mark for the organism, 1 mark for disease and 2 marks for congenital defect
Viruses, Bacteria & Protozoa Can Cause Birth Defects
Organism
Rubella Virus
Disease
German Measles
Cytomegalovirus
Cytomegalic Inclusion Disease
Trepanoma pallidum (Spirochete
bacterium)
Syphilis
Toxoplasma gondii (Protozoan)
Toxoplasmosis
Congentital Defect
Cataracts, Deafness,
Cardiovascular Defects, Slow
Growth of Fetus
Microcephaly, microphthalmia,
cerebral calcification, slowing of
intrauterine growth
Dental Abnormalities, Deafness,
Mental Retardation, Skin & Bone
Lesions, Meningitis
Microcephaly, Hydrocephaly,
Cerebral Calcification, Mental
Retardation
If they put another virus or bacteria that is not on the list, good it or ask me.
5. What is the nodal flow model. Describe the two hypotheses of the nodal flow model (15 marks).
The nodal flow model is a hypothesis of how the left-right axis (1) is established in the embryo. The
model suggests that monocilia (1) that line the cell in the node (1) rotate (1) and move the surrounding
fluid from right to left (1). There are two different hypothesis as to how nodal flow leads to left-right
axis formation. First: the morphogen gradient model (1). In this model the fluid that the monocilia
move contains morphogens (1), specifically sonic hedgehod (Shh) (1), and this movement from right to
left establishes a concentration gradient (1) of the morphogen. This way Shh is high on the left and low
on the right. Shh then leads to signaling in cell on the left side (1), with the primary effect of calcium
elevation. Second: the 2 cilia hypothesis or physical stimulation hypothesis (1). In this hypothesis the
movement of the fluid (physical force (1) stimulates the cells on the left side of the node and leads to
signaling events (1), starting with calcium elevation (1). They could also right about the 2 cilia types.
Some cilia are motile and move the fluid, others are sensory cilia that are non motile and sense the fluid
movement by being pushed or bent and this leads to opening of the calcium channels that initiates the
signaling. I only talked about this in lecture so not everyone might go into that detail so people that do
can have 1 bonus mark.
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Some people may not know the two hypotheses at all, if they didn’t attend the lecture so they might just
right out all of the details about the signaling molecules involved in the morphogen gradient
hypothesis. They should get 2 marks if they get any of the following figures and molecules right or if
they write more about them:
Here is the text from Dan’s online PDFs:
“Initially Shh is expressed uniformly in the primitive node but over time it becomes expressed predominantly on the left side. This is followed by the increased expression of Nodal (a transforming growth factor beta, TGF , family member) on the left side of the primitive node. In turn, this is followed by the expression of another TGF , family member Lefty2. Finally the transcription factor Pitx2 is activated which presumably regulates a number of genes some of which are involved in lateral plate mesoderm differentiation. Other factors such as fibroblast growth factor 8 (Fgf8) plus Lrd and Kif which are mentioned below are also involved. Do Nodal Cilia Define Symmetry?
The cell communication events mediating the development of the left axis are under analysis. Shh is a
diffusible molecule that regulates signaling events in other cells. The nodal flow model suggests that
morphogens and signaling molecules involved in defining the left-right axes is driven by the action of cilia
that cause molecules to flow from right to left across the primitive node (see arrow in above diagram). mice and other mammals, cells in the node have been shown to possess a single cilium (monocilium) and mutations that affect ciliary action such as null mutations for Lrd (which encodes ciliary dynein) alter L‐R symmetry. There are interpretations of the nodal flow model. One is that the cilia flow directs soluble morphogens and factors from right to left. While others suggest the Nodular Vesicular Particles (NVPs) are released from right cells and carried to those on the left by ciliary action. Either of these or even other events lead to higher calcium ion levels on the left which could direct left‐side cell fate 7
decisions. The nodal flow model gets support from the fact that mutations in ciliary dynein can lead to sinus inversus (i.e., right‐left switching) for various organs (e.g., heart as seen in Kartagener’s syndrome).” I realize that some people may get more than 10 marks on this question and that’s ok, I doubt though
that will happen.
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Assay. Answer in assay format. Organization, clarity, grammar and scientific language are very
important. Use the space provided. Diagrams may be used (but still need to be written about). 25
marks.
1. Describe the importance of the cytoskeleton during specific events of embryogenesis. What are the
important cytoskeletal components and what are their roles. How can you visualize them inside cells.
What are 3 specific events during embryogenesis where the cytoskeleton plays a major role. What
would a mutation in one of the cytoskeletal component genes lead to during embryogenesis (think big).
Cytoskeleton is composed of microtubule (1) made up of tubulin (1) and microfilaments (1) made of
actin (1). Cytoskeleton is responsible for giving a specific shape to the cells (1) along with other
functions like transport of intracellular components, secretion, mitosis etc (1). Cytoskeletal compoents
can be visualized through immunolocalization (antibodies) or through chemical means ex: rhodaminephalloidin. They could also explain this in a bit more detail or come up with other methods. Just judge
for yourself it their answer is good enough (2). A mutation in actin or tubulin would be detrimental and
not development would occur since cytoskeleton is so important (1).
We talked a lot about microtubules and microfilaments through the course so they could have picked
pretty much anything as the examples of the events during embryogenesis. Give 4 marks for each event
so 12 marks for 3 events. Last 3 marks are for assay format. If they write point form or unclear and not
proper scientific language then be strict and take the marks off.
Events:
Bottle cell formation during gastrulation (4), neurulation (4) and ceural crest cell formation (4)
Formation of bottle cells and mesenchyme cells…so epithelial -mesenchymal transitions. Here the
microtubules and microfilaments create the bottle cell shape of the cells that is important for the
transition, along with loss of E-cadherin. Microfilaments constrict the top and microtubules extend the
bottom. Once all cell adhesion is lost bottle cells turn in to mesenchyme cells and migrate individually.
This occurs during gastrulation when epiblast cells move through the node and the primitive streak to
form the endoderm and the mesoderm. This also happens when NCCs separate from the dorsal part of
the neural tube to migrate to their destinations. During neurulation though epithelial ectoderm cells turn
into bottle cells during neural tube formation but do not form mesenchyme cells so this event is not an
example of epithelial-mesenchymal transition but is an example of bottle cell formation. An experiment
was performed to show how important the cytoskeleton is for neurulation (so bottle cell formation).
Here tey treated cells with cytochalasin to disrupt microfilaments and showed that neurulation does not
occur. Then they treated the cells with colchicine to disrupt microtubules and also showed that
neurulation does not occur. To get full marks they should have written all of the above.
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Other events they could have written about:
Neurite outgrowth (4). Microtubules comprise the axons and microfilaments make up to the growth
cones. The growth cones dynamically sense the environment and move towards their target (target
tissue, like bicep muscle for example) and axon grows. End result is a nerve cell that communicates
with the target. The same experiment was done as above to show the importance of the cytoskeleton.
Other events:
Cell motility. Microfilaments make up the filopods in migrating cells like PGCs or NCCs. Here they
can talk about filopod extension and integrin/fibronectin interaction and subsequent contraction of the
back of the cells through myosin. This leads to cell movement. The could also mention that this is the
ability the cells acquire when they become mesenchyme cells after epithelial-mesenchymal transition
for example in gastrulation.
Other events:
They could have also just thought of the cytoskeleton in relation to cell adhesion rather than cell shape.
So if they talked about adhesion molecules linking to the cytoskeleton, for example E.-cadherin or NCAM they should also get some marks, but probably not full 4 because I don’t think they could have
written enough to for 4 marks. They could have also remembered about apoptosis and cell shrinkage,
even cleavage and microtubules being part of the spindle apparatus for cleavage and even before for
polar body formation. So give them marks for anything reasonable but not full 4 marks because again
these will likely be 1-2 sentence answers, so 1-2 marks.
If you’re not sure if something applies, ask me.
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Tutorial Section (TOTAL 15 marks)
Multiple choice. Circle the best answer. 1 mark each (TOTAL 6 marks).
1. An example of a “classical” embryology experiment is: a) Transplanting a blastopore from one embryo to another b) Co‐localizing MUPP1 and CaMKIIα to the acrosome c) Creating N­cad mutants and examining the effects on eye development d) All of the above e) None of the above 2. Which of the following involve altering an organism’s genome? a) Knock‐downs b) Knock‐outs c) Knock‐ins d) Only a and b are correct e) Only b and c are correct 3. Which of the following regarding the genes involved in eye development is NOT true? a) Bmp7 and FGF induce lens development b) Mitf regulates development of the retina pigmented epithelium c) The lens fails to develop in N‐cadherin mutants d) Pax6 is a Sry family member transcription factor involved in retina formation e) Chx10 mutations are linked to anophthalmia 4. The metallothionein promoter region (MT­1): a) Is a type of inducible promoter b) Is a type of tissue‐specific promoter c) Is activated by zinc d) Only a and c are correct e) Only b and c are correct 5. Transplantation experiments can be used to track the migration of neural crest cells by: a) Transplanting quail embryo neural tube into a chick embryo and detecting with anti‐chick antibody b) Transplanting quail embryo neural tube into a chick embryo and detecting with anti‐quail antibody c) Transplanting chick embryo neural tube into a quail embryo and detecting with anti‐quail antibody d) Only a and c are correct e) All of the above are correct 12
NAME _________________________________________
ST#_________________________
6. A “painting” experiment: a) Can determine the “fate map” of a cell b) Involves the use of morpholinos c) Can detect spina bifida d) Involves painting transgenic mice to obtain different coloured offspring e) None of the above Fill-in-the blank. Wright in full. 1 mark each. (TOTAL 2 marks).
1. The technique that visualizes the localization of a specific mRNA in a cell or tissue is known as in situ hybridization 2. Supplementation of folic acid reduces the incidence of neural tube defects Short Answer. Use the space provided. (TOTAL 7 marks)
1. What is the difference between “descriptive” and “experimental” embryology? (2 marks) • Descriptive embryology involves observation of normal development and cataloguing its events, without experimental intervention. • Experimental embryology involves experimental manipulations to study development 2. Describe the steps involved in creating a transgenic mouse by the “pronuclear injection” method. (3 marks) •
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Plasmid DNA containing the gene is injected directly into the male pronucleus of a mouse zygote Zygote is transferred to a host mother Mouse gives birth to a transgenic offspring 13
3. Which technique can you use to detect the lemon sign? What would you look for? (2 marks) • Detected using ultrasonography • Frontal bones of the cranium appear flattened, giving it a “lemon” shape THE END!!! This test is out 93 marks. Good Luck on the final exam. Do not use this extra space to answer questions. You may use it for rough work. 14