165 Critical Thinking Questions

23. Name two differences between prokaryotic and eukaryotic cells and how these differences benefit multicellular organisms.

24. Describe how controlling gene expression will alter the overall protein levels in the cell.

25. Describe how transcription in prokaryotic cells can be altered by external stimulation such as excess lactose in the environment.

26. What is the difference between a repressible and an inducible operon?

27. In cancer cells, alteration to epigenetic modifications turns off genes that are normally expressed. Hypothetically, how could you reverse this process to turn these genes back on?

28. A scientific study demonstrated that rat mothering behavior impacts the stress response in their pups. Rats that were born and grew up with attentive mothers showed low activation of stress-response genes later in life, while rats with inattentive mothers had high activation of stress-response genes in the same situation. An additional study that swapped the pups at birth (i.e., rats born to inattentive mothers grew up with attentive mothers and vice versa) showed the same positive effect of attentive mothering. How do genetics and/or epigenetics explain the results of this study?

29. Some autoimmune diseases show a positive correlation with dramatically decreased expression of histone deacetylase 9 (HDAC9, an enzyme that removes acetyl groups from histones). Why would the decreased expression of HDAC9 cause immune cells to produce inflammatory genes at inappropriate times?

30. A mutation within the promoter region can alter transcription of a gene. Describe how this can happen.

31. What could happen if a cell had too much of an activating transcription factor present?

32. A scientist identifies a potential transcription regulation site 300bp downstream of a gene and hypothesizes that it is a repressor. What experiment (with results) could he perform to support this hypothesis?

33. Describe how RBPs can prevent miRNAs from degrading an RNA molecule.

34. How can external stimuli alter post-transcriptional control of gene expression?

35. Protein modification can alter gene expression in many ways. Describe how phosphorylation of proteins can alter gene expression.

36. Alternative forms of a protein can be beneficial or harmful to a cell. What do you think would happen if too much of an alternative protein bound to the 3′ UTR of an RNA and caused it to degrade?

37. Changes in epigenetic modifications alter the accessibility and transcription of DNA. Describe how environmental stimuli, such as ultraviolet light exposure, could modify gene expression.

38. A scientist discovers a virus encoding a Protein X that degrades a subunit of the eIF4F complex. Knowing that this virus transcribes its own mRNAs in the cytoplasm of human cells, why would Protein X be an effective virulence factor?

39. New drugs are being developed that decrease DNA methylation and prevent the removal of acetyl groups from histone proteins. Explain how these drugs could affect gene expression to help kill tumor cells.

40. How can understanding the gene expression pattern in a cancer cell tell you something about that specific form of cancer?