Molecular Cell Biology Lodish 8e Ch21 Test Bank PDF

lOMoARcPSD|46169929 Molecular Cell Biology Lodish 8e Ch21 Test Bank molecular biology (Yonsei University) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by girasol rey (stfuplease...

lOMoARcPSD|46169929 Molecular Cell Biology Lodish 8e Ch21 Test Bank molecular biology (Yonsei University) Scan to open on Studocu Studocu is not sponsored or endorsed by any college or university Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 1 21 Cell Birth, Lineage, and Death Section 21.1 1. In mammalian development, which of the following is the correct chronological order of events? a. blastocyst, zygote, four-cell, compacted morula, b. zygote, four-cell, compacted morula, blastocyst c. compacted morula, blastocyst, zygote, four-cell d. four-cell, compacted morula, blastocyst, zygote Ans: b Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Easy 2. Describe gamete fusion that occurs during mammalian fertilization. Ans: The mouse sperm must penetrate a layer of cumulus cells before it encounters the amorphous zona pellucida (ZP) layer surrounding the oocyte. It is here where the sperm surface protein GaIT encounters and binds ZP3 glycoprotein in the ZP, which triggers the acrosomal reaction. The acrosomal vesicle, containing hydrolytic and proteolytic enzymes and present within the tip of the sperm head, is exocytosed as a result of the acrosomal reaction. These enzymes serve to degrade the ZP, facilitating sperm- egg plasma membrane interactions. Sperm penetration triggers a Ca2+ release from within the egg, triggering the exocytosis of egg cortical granules. Enzymes within these granules alter the properties of the ZP to prevent the binding of additional sperm (polyspermy). Question Type: Essay Chapter: 21 Blooms: Applying Difficulty: Difficult 3. How can somatic cell nuclear transfer be used to clone a mouse? Ans: Although a relatively inefficient method of cloning, as evidenced from the data that emerged following cloning Dolly the sheep, the technique relies on removing the nucleus from a fully differentiated cell and transplanting it into an enucleated egg of a donor mouse. In one example, the nucleus from an olfactory sensory neuron of a mouse that expresses green fluorescent protein (GFP) was transplanted into an enucleated egg and then differentiated in culture until the inner cell mass stage. GFP-expressing ES cells were isolated and injected into a tetraploid blastocyst host. When this chimeric blastocyst was transplanted into the uterus of a pseudopregnant female, the tetraploid cells formed the placenta and the GFP-expressing cells the embryo proper. If all cells express GFP when the pups were born, this would indicate that their nuclei had been derived from that originally isolated from the GFP-expressing olfactory neuron. Question Type: Essay Chapter: 21 Blooms: Understanding Difficulty: Difficult 4. The first differentiation event following fertilization occurs when: a. the morula separates from the blastocyst. b. the trophoectoderm separates from the inner cell mass. Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 2 c. the four-cell stage undergoes cleavage to generate the eight-cell stage. d. the zygote divides to form two cells. Ans: b Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Easy Section 21.2 5. In the mouse embryo, pluripotent stem cells are found in the: a. inner cell mass. b. trophectoderm. c. zona pellucida. d. blastocoel. Ans: a Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Easy 6. Daughter cells that form as a result of asymmetric cell division may differ in: a. size. b. shape. c. protein composition. d. all of the above Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Easy 7. Which of the following genes are expressed exclusively in pluripotent embryonic stem cells? a. Nanog b. Sox2 c. Oct4 d. Nanog and Oct4 Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Moderate 8. Fully differentiated mouse fibroblasts can be reprogrammed or induced to form pluripotent stem cells when transfected with retroviral vectors that express: a. KLF4. b. c-MYC. c. SOX2. d. all of the above Ans: d Question Type: Multiple choice Chapter: 21 Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 3 Blooms: Remembering Difficulty: Moderate 9. Dolly, the famous sheep, was cloned using: a. induced pluripotent stem cells. b. homologous recombination. c. somatic cell nuclear transfer. d. Cre recombinase. Ans: c Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Easy 10. Briefly describe how Yamanaka and colleagues induced differentiated cells to form stem cells. Ans: Research had shown that certain transcription factors (KLF4, SOX2, OCT4, and c-MYC) were expressed in embryonic stem cells, and down-regulation of their expression coincided with differentiation into one of the three germ layer lineages. Recognizing this, Yamanaka infected mouse fibroblasts with retroviruses expressing these transcription factors and found that the cells lost their fibroblast-like properties and adopted characteristics of stem cells. Later on, these experiments were repeated using keratinocytes (skin cells) that were repeatedly transfected with specific mRNAs encoding the four canonical transcription factors described above. Over time, these cells adopted a stem cell fate, and there was no trace of the introduced mRNAs, indicating that they had in fact been reprogrammed. Question Type: Essay Chapter: 21 Blooms: Applying Difficulty: Difficult 11. The use of cell-based models to understand or treat human disease processes is aided by stem cells in all the following ways, except: a. growth of neurons in cell culture containing mutations associated with ALS for drug screening. b. culture of patient-specific cells to replace those lost to disease, such as for type 2 diabetes. c. differentiation of neurons from iPS cells to replace those damaged by neurodegenerative diseases. d. provides proof that ES cells are pluripotent and can divide to make a normal animal. Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Moderate Section 21.3 12. In the Drosophila ovary, which of the following proteins is secreted from the cap cell and is responsible for creating and maintaining the niche for germ-line stem cells? a. Hedgehog b. FGF c. Arm d. Ptc Ans: a Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Easy Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 4 13. Which of the following is FALSE regarding the stem cells located in the epithelial lining of the small intestine? a. They express -catenin. b. Lgr5 encodes an R-spondin receptor. c. The Lgr5 gene is induced by Wnt signaling. d. They are located in pits called crypts. Ans: b Question Type: Multiple choice Chapter: 21 Blooms: Applying Difficulty: Moderate 14. Which of the following is(are) in the cell lineage that gives rise to T cells? a. GM-CFC b. myeloid stem cell c. pluripotent hematopoietic stem cell d. myeloid stem cell and pluripotent hematopoietic stem cell Ans: c Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Moderate 15. Floral meristems give rise to: a. leaves. b. petals. c. stamens. d. petals and stamens. Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Moderate 16. Describe how the stem cell niche contributes to the maintenance of germ-line stem cells in Drosophila. Ans: In the fly ovary, there is a niche where oocyte precursors form and begin to differentiate. Cap cells in the tip of the germarium secrete two TGF--like proteins (Dpp and Gbb) as well as Hh. Binding of these ligands to TGF-  receptor I and II, and Ptc, respectively, on the surface of a germ-line stem cell, signals two transcription factors Mad and Med and a co-repressor Schnurri, to repress expression of the bag of marbles (bam) gene, which encodes a key differentiation factor. The maintenance of the niche is dependent on homotypic E-cadherin inteactions between cap cells and germ-line stem cells, and armadillo, the fly homolog of -catenin, which tethers E-cadherin to the actin cytoskeleton within each cell type. When a germ-line stem cell divides, the daughter cell that maintains the E-cadherin-association with the cap cell continues its life as a stem cell. The other daughter cell, however, is displaced from the Dpp, Gbb, and Hh signals, allowing the Bam gene to be expressed. Translation of Bam in this cell induces it to differentiate into a cystoblast, which after four rounds of division, produces 16 interconnected cells, one of which becomes the oocyte. Question Type: Essay Chapter: 21 Blooms: Understanding Difficulty: Difficult 17. Describe how Cre recombinase is used in lineage-tracing studies to follow the fate of Lgr5 +-expressing intestinal stem cells. Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 5 Ans: Investigators have genetically engineered a strain of mice in which Cre recombinase fused to the estrogen-binding domain of the estrogen receptor is placed under the control of the Lgr5 promoter. The Cre recombinase-ER chimera would therefore only be expressed in intestinal stem cells of these mice, and the protein would be localized to the cytoplasm. Treating these cells, however, with the estrogen analog tamoxifen causes this fusion protein containing the domain of the estrogen receptor to translocate to the nucleus. Another strain of mice was engineered to express the bacterial -galactosidase (-gal) gene preceded by two loxP sites flanking a blocking segment of DNA. Thus, in the absence of Cre recombinase, there would be no -gal expression. Mice from the two strains were mated, and offspring containing both marker transgenes were identified. Only mice treated with tamoxifen showed -gal expression in cells of the intestinal crypt. In this manner, tamoxifen had facilitated the translocation of the Cre-ER chimeric protein into the nucleus, where Cre had interacted with the loxP sites to excise the blocking segment of DNA. The -gal gene was then capable of being expressed, and when the protein was translated, it was detected using a histochemical stain in which a substrate in contact with -gal forms a blue precipitate. In the lineage-tracing experiment, mice exposed to tamoxifen for 1 day showed blue staining in cells deep in the intestinal crypt. Those exposed to tamoxifen for longer periods showed blue- stained cells higher up in the villus, indicating that they had migrated away from their “birthplace.” Question Type: Essay Chapter: 21 Blooms: Applying Difficulty: Difficult 18. Define stem cells. Which of the following cells are stem cells: (a) fertilized egg, (b) intestinal crypt cell, (c) granulocyte- macrophage colony-forming cell (GM-CFC)? Ans: Stem cells are cells that can both give rise to differentiated cell types or their precursors and self-renew. Stem cells are found in both embryonic and adult tissues. (a) The fertilized egg is not really a stem cell. It gives rise to all cell types in an animal but does not self-renew. (b) Within the intestinal crypt, there is a population of true stem cells that give rise to all intestinal epithelial cells and can self-renew. (c) GM-CFCs are progenitor cells, not stem cells. They can give rise to multiple differentiated blood cells but cannot self-renew. Myeloid stem cells are the stem cells for this lineage. Question Type: Essay Chapter: 21 Blooms: Applying Difficulty: Difficult 19. Which of the following provides evidence for the role of Paneth cells in supporting the intestinal stem cell niche? a. Mutant mice with reduced numbers of Paneth cells have fewer intestinal stem cells. b. Co-culture of Paneth cells with intestinal stem cells leads to formation of villus-like structures. c. Paneth cells produce Wnt. d. all of the above Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Easy Section 21.4 20. The mating projection or shmoo in budding yeast cells relies on having: a. Cdc42 recruited and localized to the region near the highest concentration of mating pheromone. b. formin proteins to nucleate the assembly of actin filaments. c. myosin V to move secretory vesicles to the plus (+) ends of microfilaments. d. all of the above Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Applying Difficulty: Moderate Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 6 21. Even before the first cell division, the one-cell C. elegans zygote has an asymmetric distribution of: a. Par3 and aPKC in the cortex of the posterior half of the cell. b. Par6 in the cortex of the posterior half of the cell. c. Par2 in the cortex of the posterior half of the cell. d. all of the above Ans: c Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Moderate 22. In C. elegans, which of the following is located in the lineage that gives rise to germ cells? a. P1 b. P2 c. P3 d. all of the above Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Moderate 23. The apical-basolateral polarity of epithelial cells depends on which one of the following? a. the Scribble complex in the apical domain of the cell b. the Crumbs complex in the basal domain of the cell c. the interaction between nectin and JAM-A d. all of the above Ans: c Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Moderate 24. Which is the correct combination of proteins in polarized cells involved in planar-cell polarity? a. Flamingo-Strabismus on one side and Dishevelled-Frizzled on the other b. Frizzled-Strabismus on one side and Flamingo-Dishevelled on the other c. Strabismus-Dishevelled on one side and Flamingo-Frizzled on the other d. none of the above Ans: a Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Moderate 25. Shmoo formation allows budding yeast to grow toward a concentration of mating factor. Describe how asymmetric changes in the haploid yeast cell promote the formation of this mating projection. Ans: Haploid yeast exist in either an a or  state, where a cells secreting a factor prefer to mate with  cells secreting  factor. Each cell type expresses a surface G-protein coupled receptor (GPCR) for the other type’s mating factor, and when the factors are detected, each cell synchronizes their cell cycle and arrest at G o. GPCR activation results in the accumulation and activation of the small G-protein Cdc42 closest to the highest concentration of the mating factor. Cdc42, now in the active GTP-bound state, activates formin proteins that promote the assembly and elongation of microfilaments that have their (+) ends directed toward the cell cortex. Secretory vesicles, carried by the myosin-V motor protein toward the (+) end of these microfilaments, promote the Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 7 localized growth of the projection (shmoo). Cdc42 that has moved away from the growing tip as a result of this increase in outward growth gets endocytosed and transported back to the shmoo tip, where it can continue to participate in formin activation and microfilament assembly. When shmooing cells of opposite mating types eventually touch, they fuse at the shmoo tips, and the haploid nuclei combine to restore the diploid state. Question Type: Essay Chapter: 21 Blooms: Understanding Difficulty: Difficult 26. Describe two ways that stem cells can be induced to divide asymmetrically. Ans: In the first method, a stem cell responds to an external cue by becoming polarized, causing fate determinants to localize to one region of the cell. The daughter cell inheriting these determinants remains a stem cell, whereas the other daughter cell differentiates. The other method involves a niche, which causes the stem cell to orient its mitotic spindle. Following division, the daughter cell in association with the niche remains as a stem cell, whereas the one distant to the niche differentiates. Question Type: Essay Chapter: 21 Blooms: Applying Difficulty: Moderate 27. Epithelial cell tight junctions recruit: a. Crumbs complexes. b. Scribble complexes. c. apical PAR complexes. d. all of the above Ans: c Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Easy 28. When a cell divides asymmetrically: a. PAR proteins are spread homogenously throughout the cell. b. the spindle orients the new daughter cell toward the niche cell. c. exogenous factors bind cell surface receptors to induce actin cytoskeletal rearrangements. d. the resulting two cells are identical to each other. Ans: c Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Easy Section 21.5 29. Which of the following is a feature that defines a cell dying in response to tissue damage (necrosis)? a. The nucleus condenses and then fragments. b. Small membrane bodies are released and then engulfed by other cells. c. The cell shrinks. d. none of the above Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Moderate Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 8 30. Which of the following genes encodes a caspase in C. elegans? a. ced-3 b. ced-4 c. ced-9 d. ced-8 Ans: a Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Easy 31. Which of the following apoptotic proteins is homologous to human Bcl-2? a. CED-3 b. CED-4 c. CED-9 d. none of the above Ans: c Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Moderate 32. Which of the following forms a dimer that gets displaced from the surface of the mitochondria by EGL-1? a. CED-3 b. CED-4 c. CED-9 d. CED-8 Ans: b Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Moderate 33. Which of the following triggers apoptosis? a. Fas ligand b. NGF c. TNFα d. Fas ligand and TNFα Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Moderate 34. Explain the role of mitochondria in apoptosis. Ans: When mitochondria are triggered to release cytochrome c into the cytosol, cytochrome c binds to and activates Apaf-1, which leads to activation of the caspases. Release of cytochrome c release occurs when Bax homodimers form channels that permit ion influx through the mitochondrial membrane. Bax can also promote apoptosis in a caspase-independent manner that involves mitochondrial depolarization. Question Type: Essay Chapter: 21 Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 9 Blooms: Understanding Difficulty: Moderate 35. Apoptosis can be induced by a mitochondrial protein being released into the cytosol. This protein binds directly to what in the cytosol? a. caspase 3 b. Bax c. Bcl-2 d. Apaf-1 Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Remembering Difficulty: Easy 36. Mitochondrial permeabilization can be induced by compounds that poke small holes in the outer membrane. This would cause: a. cytochrome c to be released into the cytosol. b. increased ATP synthesis through oxidative phosphorylation. c. increased Bad-Bcl2 interactions. d. upregulation of caspase expression. Ans: a Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Moderate 37. Examination of a cell’s structure reveals condensed chromatin, a shrunken cytoplasm, but unfragmented DNA and a lack of blebbing. If this cell has been triggered to undergo apoptosis by an extrinsic factor, which of the following events has NOT likely happened yet? a. activation of a TNF-α receptor b. recruitment of TRADD c. recruitment of FADD d. activation of caspases Ans: d Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Easy 38. XIAP proteins: a. inhibit initiator and effector caspases. b. are released from the mitochondria through Bad/Bax oliogomers. c. are activated by SMAC/DIABLO proteins. d. cleave the cytoskeleton during apoptosis. Ans: a Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Easy Downloaded by girasol rey ([email protected])  lOMoARcPSD|46169929 21 - 10 39. In cells that have been signaled to die via TNF-a receptor signaling but lack caspase-8 activity: a. apoptosis occurs via the other caspases. b. necroptosis occurs downstream of RIP protein activation of MLKL. c. the cell remains alive and viable. d. none of the above Ans: b Question Type: Multiple choice Chapter: 21 Blooms: Understanding Difficulty: Easy Downloaded by girasol rey ([email protected])