Practice test 3 2022
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Practice test 3 2022
SECTION A
1 Which of the following molecules is NOT a constituent part of the extracellular matrix?
a. Collagen
b. Hyaluronan
c. Laminin
d. Aggrecan
e. Integrin
2 In animal tissues, the relative amounts of collagens and glycosaminoglycans (GAGs) varies depending upon the nature of the tissue. Which of the following statements is TRUE concerning the composition of tendons and vitreous humour (the transparent jelly found inside the eyeball)?
a. Tendons are mainly composed of GAGs, with little collagen
b. Tendons contain broadly equal amounts of GAGs and collagen
c. Vitreous humour is mainly composed of GAGs, with little collagen
d. Vitreous humour contains broadly equal amounts of GAGs and collagen
e. Neither tendons nor vitreous humour contain GAGs
3 The following statements are about adherens junctions. Which of the statements is FALSE?
a. Cell-cell attachment at adherens junctions is mediated by cadherins
b. Of the major cell-cell junction types, adherens junctions contribute the most to the polarisation of epithelial cells
c. Adherens junctions allow sheets of epithelial cells to bend into tubes
d. A continuous belt of actin cytoskeleton across the epithelial sheet is linked by adherens junctions
e. Adherens junctions support mechanical cell-cell attachment
4 Which of the following statements about cyclins is TRUE?
a. cyclins all rise in concentration at the start (M-G1 transition) of the cell cycle
b. no cyclin is present in mitosis
c. cyclins are protein kinases
d. cyclins bind to cdks
e. no cyclin is present in S phase
5 Which one of the following best describes the foetuses potentially at risk of foetal transfusion syndrome?
a. Any human foetus in any mother
b. Any human foetus in a mother who is receiving or who has recently received a blood transfusion
c. Any type of twin (when a foetus)
d. Only one of two twins, of any type of twinning (when a foetus)
e. Only one of two identical twins (when a foetus)
6 Which of the following statements best describes mechanical forces, and cellular responses to them, in human skin?
a. Mechanical tension is a short-range force and it inhibits cell division
b. Mechanical tension is a short-range force and it activates cell division orthogonally to the force vector
c. Mechanical tension is a short-range force and it activates cell division along the force vector
d. Mechanical tension operates equally across a stretched tissue and it activates cell proliferation along the force vector
e. Mechanical tension operates equally across a stretched tissue and it activates cell proliferation orthogonally to the force vector
7 In plant leaf stomata differentiation, what is the order of cell types in development?
a. meristemoid – protoderm mother cell – guard mother cell – guard cell
b. meristemoid – protoderm – guard cell – guard mother cell
c. protoderm – pavement cell – guard cell – KAT1 cell
d. protoderm – meristemoid – guard mother cell – guard cell
e. KAT1 cell – meristemoid – pavement cell – guard mother cell
8 What are the conditions required for initial MyoD gene activation during muscle differentiation?
a. Pax6 and Myogenin are both present in the cell
b. Growth factors are removed
c. Growth factors are present (signal) and Pax3 expression is absent
d. Cyclins are degraded
e. Pax3 and Myf5 are both present in the cell
9 An organiser is:
a. A gene that is expressed in a developing embryo and instructs the formation of an adult structure
b. A gene that is expressed in a developing embryo and inhibits the formation of an adult structure
c. A group of cells that receives signals from nearby embryonic tissue and develops into an adult structure
d. A group of cells that sends signals to nearby embryonic cells instructing them to develop into adult structures
e. A group of cells that must die in order for the rest of the organism to survive
10 Which of these terms best describes signalling between two or more cells 0.1mm apart in a biological tissue?
a. Juxtacrine
b. Paracrine
c. Endocrine
d. Autocrine
e. Intracrine
11 Different types of cells in the crypt of the gut normally segregate from one another by which mechanism?
a. Contact mediated repulsion
b. Lateral inhibition
c. Ectopic gene expression
d. The ‘French Flag’ model
e. Autocrine signalling
12 Which of the following statements about the role of GDNF in kidney development is correct?
a. It is expressed in the ureteric bud and signals to induce nephron formation
b. It is expressed in the metanephric mesenchyme and signals to induce ureteric branching
c. It is expressed by podocytes and signals to induce vasculogenesis
d. It is expressed in the ureteric trunk and signals to supress supernumerary branching
e. It is expressed in the metanephric mesenchyme and where it induces condensation of the mesenchyme
13 Convergent extension movements in developing renal epithelia:
a. Increase the length and decrease the circumference of tubules
b. Increase the length and circumference of tubules
c. Decrease the length and the increase circumference of tubules
d. Decrease the length and circumference of tubules
e. Do not change the length but the increase circumference of tubules
14 Which of these statements best describes the mammalian body’s need for stem cells?
a. Some tissues are composed of many cell types so need a source of multipotent cells, which stem cells can provide
b. Stem cells are needed in adult tissues that renew themselves quickly, but stem cells themselves need not be fast-dividing
c. Stem cells divide very fast so are needed for tissues that renew themselves quickly
d. Stem cells are only present in early embryos, where they provide the source of all differentiated cells
e. Stem cells are needed because all adult tissues need to renew themselves
15 Which one of the following tissues are thought NOT to be renewed by stem cells in adult mammals?
a. Muscle
b. Gut
c. Lens of the eye
d. Brain
e. Blood
16 Which of the following statements is TRUE about the relationship between all stem cells and their niches?
a. The niche provides a physical environment for stem cell self-renewal
b. The niche causes its associated stem cell(s) to divide asymmetrically to give one stem cell and one differentiated cell
c. Stem cells are anchored to the niche via a spectrosome
d. Wnt signalling from the niche is necessary for stem cell self-renewal
e. Niches are cells supported by stem cells
17 In neural tube development, what role does SHH signalling play?
a. SHH patterns ventral cell fates via a gradient from the floor plate
b. SHH is required for midbrain formation
c. SHH patterns dorsal cell fates via a gradient from the roof plate
d. SHH patterns anterior neural tube fates via a gradient from the telencephalon
e. SHH signalling causes the death of dopaminergic neurons
18 Which developing brain regions can directly produce dopaminergic (DA) neurons?
a. Only the midbrain
b. All brain regions
c. Only the hindbrain
d. Midbrain and hindbrain
e. Only the lateral regions
19 Concerning choanoflagellates, which one of the following statements is FALSE:
a. Choanoflagellates are single-celled organisms most closely related to animals (metazoa)
b. Choanoflagellates use a collar of actin-rich filaments to catch their food
c. Choanoflagellates are free-swimming phagocytotic organisms that eat other eukaryotes
d. Choanoflagellates can sometimes form multi-cellular colonies in particular environmental conditions
e. Choanoflagellates have an axis of asymmetry
20 Which one of the following statements concerning WNT signalling is FALSE?
a. β-catenin is stabilised by an active WNT signal
b. WNT is a secreted ligand
c. WNT signalling can cause changes in gene expression and cell shape
d. WNT signalling is present in unicellular choanoflagellates
e. TCF is a transcription factor that is inactive unless bound by β-catenin
SECTION B
A.
CO and FT proteins mediate flowering in response to day length in Arabidopsis.
1 Which statement best describes the mechanism?
a. Long days result in increased CO levels in the leaf which in turn promote synthesis of FT
protein. FT protein travels from the leaf in the sap throughout the plant and induces flower formation only in the shoot.
b. Long days result in increased FT levels in the leaf which in turn promote synthesis of CO
protein. CO protein travels from the leaf in the sap throughout the plant and induces flower formation only in the shoot.
c. Long days result in increased CO levels in the shoot which in turn promote synthesis of FT protein which then induces flower formation in the shoot.
d. Long days result in increased FT levels in the shoot which promote synthesis of CO protein which then induces flower formation in the shoot.
e. Long days result in increased CO levels in the leaf, CO protein then travels in the sap to the shoot where it promotes synthesis of FT protein which in turn induces flower formation in the shoot.
B.
There is a genus of frogs that is normally diploid, but tetraploid individuals are viable. The cells of the tetraploid animals are larger than those of the diploid (about twice the volume). The overall size of the mature animals is about the same, as is the timing of their development. A group of students is discussing these observations, and different students come out with different ideas about how DNA content, cell size and animal size might be controlled and related in these animals.
2. Here are the suggestions of each student. Which is the only one student that has made suggestions entirely compatible with the data above?
a. Cell size may reflect DNA/cytoplasm ratio, organism growth limit cannot be set by counting cell divisions
b. Cell size may reflect DNA/cytoplasm ratio, organism growth limit may be set by counting cell divisions
c. Copying twice as much DNA takes twice as much time, so cells grow twice as large per cycle and the cycles take twice as long, so we end up with an animal with half the number of cells at the normal time of maturity
d. Cell growth is less efficient in tetraploid cells, therefore cells are larger
e. Organism size is determined by the ratio of DNA content to cell surface area, and this does not change in tetraploid individuals
C.
People who lack a specific type of integrin on white blood cells (leukocytes), or in which the
activation of this integrin is defective, develop a rare disorder called leukocyte adhesion deficiency (LAD). A different subtype of LAD disorder occurs in people with genetic alterations in selectin
ligands (the carbohydrates that selectins bind) on leukocytes. Patients with either type of LAD suffer from repeated bacterial and fungal infections.
3. LAD type I results from loss or decreased expression of a leukocyte integrin. Which of the following functional consequences would you expect to result from LAD type I?
a. Defective initial binding of leukocytes to blood vessel endothelial cells
b. Defective tight adhesion of leukocytes to blood vessel endothelial cells
c. Defective rolling of leukocytes along blood vessel endothelial cells
d. Enhanced leukocyte invasion through blood vessel endothelium
e. No functional consequences for leukocytes
4. LAD type II results from glycosylation defects in selectin ligands (which bind selectins). Which one of the following statements about selectins is FALSE?
a. Selectins are connected to the actin cytoskeleton via anchor proteins
b. Selectins mediate cell-cell attachment in the bloodstream
c. Blood vessel endothelial cells switch on cell-surface expression of selectins at sites of inflammation
d. Selectins are conformationally activated by binding to extracellular matrix ligands or the cytoskeleton
e. Selectins are important for the recruitment of leukocytes to sites of inflammation
D.
You are studying the development of a simple ‘tube-like’ organ in a hypothetical creature. By observing what happens during normal development you discover the tube differentiates into three regions composed of distinct cells: A-, B- and C-type cells, which are in turn distinct from D-type cells found some distance from the organ (Fig. 1 below: normal).
You hypothesize that cells surrounding the organ —a patch of black cells to the left and a patch of grey cells above —contribute to the pattern of cells in the developing tube. To test this hypothesis, you surgically remove either the black cells (experiment 1) or grey cells (experiment 2) in a period
before the tube cells differentiate, then you let the creature develop further, and finally you assess how this affects the development of the tube.
5. Based on the results of experiments 1 and 2 shown in Fig. 1, which one of these statements is FALSE?
a. Grey cells are required for normal tube development
b. Black cells are required for normal tube development
c. The data are consistent with grey cells being the source of a morphogen gradient that patterns cell differentiation within the tube
d. The data are consistent with black cells being the source of a morphogen gradient that patterns cell differentiation within the tube
e. Cell type D is the default fate for the tube cells in the absence of any signals from surrounding cells
6. You conduct two further experiments (3 and 4 in the figure below).
In Experiment 3, the black cells are transplanted to the other end of the developing tube.
In Experiment 4, the grey cells are surgically removed and the black cells transplanted to the other end of the developing tube.
6. What is the most likely outcome of each experiment in terms of pattern of cells in the tube (from left to right)?
a. Expt 3: C B A; Expt 4: D D D
b. Expt 3: C B A; Expt 4: C C C
c. Expt 3: A B C; Expt 4: D D D
d. Expt 3: A B C; Expt 4: C B A
e. Expt 3: A B C; Expt 4: C C C
E.
In an experiment to understand how chicken wings develop, the apical ectodermal ridge (AER) was surgically removed after 3 days of development. After a few more days of development, a severely truncated wing was observed. In a control experiment, removing the AER and then immediately replacing it did not impair subsequent wing development.
7. What conclusion about the normal function of the AER can be drawn from this experiment alone?
a. AER signals to nearby cells, which differentiate into a limb
b. Nearby cells signal to AER, which differentiates into a limb
c. The AER grows to form part or all of the limb
d. The AER is important for wing formation, but it is not possible to conclude how
e. The AER is completely dispensable for wing formation
8. In a follow-up experiment you find that if the AER is replaced with an FGF4-soaked bead, this
prevents wing truncation and a normal wing is formed. What conclusion about the normal function of the AER can be drawn?
a. AER signals to nearby cells, which differentiate into a limb
b. Nearby cells signal to AER, which differentiates into a limb
c. The AER grows to form part or all of the limb
d. The AER is important for wing formation, but it is not possible to conclude how
e. The AER is completely dispensable for wing formation
2023-08-04