14. Which of the following is an example of eukaryotic gene regulation at the le

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14. Which of the following is an example of eukaryotic gene regulation at the level of the genome? (1 point) a. mRNA degradation b. protein degradation c. regulation by transcription factors Wh d. DNA methylation e. protein folding 15. You are interested in decreasing the expression of an oncoprotein in some cancer cells you are culturing for your Masters degree. Describe at least one approach you could take to experimentally alter gene expression in those eukaryotic cancer cells. (2 points) 16. What statement regarding signal transduction is true? (1 point) Lipids can serve as ligands to initiate signal transduction. b. a. For every one molecule of ligand that binds to a receptor, exactly one molecule of the second messenger will be activated c. Each signaling pathway is activated by a unique receptor. For example, the Erk/MAPK pathway is activated only by insulin-like growth factor 1 (IGF-1). d. Activation of a signaling pathway always leads to a change in gene expression. e. Signaling pathways operate linearly and do not interact with one another 17. Epidermal growth factor (EGF) binds to a receptor tyrosine kinase known as EGF receptor (EGFR). Which of the following is true of the EGFR? (1 point) a. The receptor contains seven transmembrane domains b. The receptor interacts with second messengers at the ligand-binding domain. c. The ligand directly phosphorylates proteins that contain SH2 domains d. EGF phosphorylates the EGFR at the kinase domain. e. EGFR has a kinase domain that phosphorylates tyrosine residues on the receptor after a ligand binds Cholera toxin is produced by the bacterium Vibrio cholerae. Exposure to this toxin leads to large losses of water and sodium from the cells that line the intestines, and results in dehydration and possibly death. Based on the information given above and your knowledge of signaling through G protein-coupled receptors (GPCRs), answer the following questions. 18. The figure on the right shows the effect of cholera toxin on GTPase activity in the presence and absence of a receptor agonist. (GTPase is the enzyme that converts GTP to GDP) a. What is true of GTPase activity when there is no receptor agonist? (1 with receptor agonist o without receptor agonist 12 point) 1? What is true of GTPase activity when there is a receptor agonist present? Explain why. (2 points) b. E 8 6 In the presence of a receptor agonist, what effect does cholera toxin have on GTPase activity? (1 point) c. 0 0.6 24 12 60 Cholera toxin ug/ml

Explanation / Answer

14. d. DNA methylation.

At genomic level, DNA methylation regulates gene expression by switching them ON/OFF (epigenetic modification). However it is present in prokaryotes but their purpose is to protect self DNA from restriction digestion as a mechanism of restriction modification.

15.

RNA interference can be one strategy to alter the gene expression by silencing the mRNA transcribed from oncoprotein.

16.

a. Lipids can serve as ligands to initiate signal transduction.

17.

e. EGFR has a kinase domain that phosphorylates tyrosine residues on the receptor after a ligand binds.

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