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Geisinger Commonwealth School of Medicine
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This document contains questions and answers from a cell biology test. The questions cover topics on Notch signaling, Wnt signaling, Hedgehog signaling, and the central dogma of molecular biology.
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1. Which of the following description is characteristic of Notch signaling? A. Lateral inhibition: a process, via which isolated single cells in a population of precursor/identical cells commit to a fate; these “specialized” cells inhibit their neighbors from acquiring the fate. B. Lateral inhibiti...
1. Which of the following description is characteristic of Notch signaling? A. Lateral inhibition: a process, via which isolated single cells in a population of precursor/identical cells commit to a fate; these “specialized” cells inhibit their neighbors from acquiring the fate. B. Lateral inhibition: a process, via which multiple cells in a population of precursor/identical cells commit to a fate; these “specialized” cells always promote their neighbors to acquire the same fate. C. Lateral promotion: a process, via which multiple cells in a population of terminally differentiated cells commit to a new fate; these “specialized” cells always promote their neighbors to acquire the same fate. D. Lateral promotion: a process, via which multiple cells in a population of terminally differentiated cells commit to a new fate; these “specialized” cells inhibit their neighbors from acquiring the same fate. Answer: A 2. Binding of _____ to Notch induces a second cleavage in the extracellular domain, and a third cleavage releases the intracellular domain. A. Delta (Dll) B. APC C. Wnt D. Hedgehog E. Notch receptor Answer: A 3. Which of the following is most correct about Notch signaling? A. Notch low cell inhibits Notch in the Notch low cell, while the interaction keeps Dll high in the Notch high cell. B. Notch high cell inhibits Notch in the Notch low cell, while the interaction keeps Dll low in the Notch low cell. C. Dll low cell inhibits Notch in the Notch high cell, while the interaction keeps Notch high in the Notch low cell. D. Notch high cell inhibits Notch in the Notch low cell, while the interaction keeps Dll low in the Notch high cell. Answer: D 4. Controlled proteolysis of ______is essential for the control of canonical Wnt signaling. A. beta-catenin B. Notch C. delta D. Delta (Dll) E. APC Answer: A 5. A reagent that inhibits glycogen synthase kinase-3β (GSK-3β) would most likely promote _______. A. beta-catenin degradation and increase Wnt signaling B. beta-catenin degradation and inhibit Wnt signaling C. beta-catenin stability and inhibit Wnt signaling D. beta-catenin stability and increase Wnt signaling Answer: D 6. In the absence of Hedgehog _____, and when Hedgehog binds to Patched, _____ A. Wnt signaling is stimulated; Wnt signaling is repressed. B. Ci is processed and represses transcription; Ci is unprocessed and activates transcription. C. Ci is processed and activates transcription; Ci is unprocessed and represses transcription. D. Notch receptor is cleaved; Dll is degraded. E. Hedgehog is angry; Hedgehog curls up into a ball. Answer: B 7. In response to inflammation, active _____ turns on gene transcription. A. NF-κB B. beta-catenin C. Delta (Dll) D. Notch E. Hedgehog Answer: A 8. Please hypothesize why mutations that deregulate Wnt signaling often cause cancer. Answer: Continuous activation of cell-growth genes in inappropriate contexts causes uncontrolled cell proliferation. 9. What is the typical flow of information in the central dogma (start to finish is left to right)? A. Protein to RNA to DNA B. DNA to RNA to protein C. RNA to DNA to protein D. Protein to DNA to RNA E. DNA to protein to RNA Answer: B 10. Which sequence of informational flow describes reverse transcription? A. RNA to DNA B. DNA to RNA C. RNA to protein D. DNA to protein E. Protein to RNA Answer: A 11. The addition of a poly-A tail to the mRNA is a part of which step? A. DNA replication B. RNA transcription C. RNA processing D. Reverse transcription E. Protein synthesis Answer: C 12. Which of the following is directly involved in the synthesis of proteins? A. the ribosomes B. the nucleus C. the Golgi apparatus D. the plasma membrane E. DNA strands Answer: A 13. In what step of the informational flow (as described by the central dogma) are the “response elements” involved? A. Reverse transcription B. DNA replication C. RNA processing D. Protein synthesis E. RNA transcription Answer: E 14. Based on the central dogma, which event is required for protein synthesis to take place in eukaryotic cells? A. The messenger RNA must translocate from the nucleus to the cytoplasm. B. The DNA must translocate from the nucleus to the cytoplasm. C. The DNA must translocate from the cytoplasm to the nucleus. D. The messenger RNA must translocate from the cytoplasm to the nucleus. E. The ribosomes must be processed with a poly-A tail. Answer: A