Lecture 13: Additional levels of control over gene expression
1. Describe three distinctly different examples of gene amplification.
2. What is meant by the term alternative splicing and what is its biological and genetic significance?
3. What is the importance of controlling the relative stabilities of mRNA molecules coding for different proteins?
4. Distinguish between end product repression and feedback inhibition in a manner that makes it clear you know what each is and how they differ.
5. Describe three distinctly different ways in which the rate of synthesis of the amino acid tryptophan is regulated in bacteria such as E. coli. (If you have trouble with this, see page 246 of the textbook).
6. Identify as many different points as you can between genomic DNA and the final functional gene product at which gene expression can potentially be regulated.
a. In prokaryotic cells.
b. In eukaryotic cells
7. Under what conditions is it advantageous for proteins and their mRNAs to have very short half lives?
8. Compare the relative advantages and disadvantages of a control system that acts early in the pathway of information flow (such as transcriptional control) and a control system that acts late in the pathway of informaiton flow (such as feedback inhibition). Be sure to take into account diverse factors such as relative expenditures of energy, speed of response, and overall effectiveness of the control mechanisms.
9. Describe as many distinctly different situations as you can in which an allosteric change in a protein alters its biological activity.
10. Describe an experiment in which the presence of an excess of one amino acid caused cultured cells to require supplementation with a different amino acid in order to be able to grow. What was the explanation for this phenomenon? How was this phenomenon used to select for mutant strains that would produce larger amounts of the first amino acid? (see example 8.5 if you need help with this one).
11. Gene amplification is used by some species to facilitate the prodction of very large amounts of the products coded for by certain genes. Mammals typically do not use gene amplification to achieve this goal. Cite as many alternative mechanisms as you can think of that are used to achieve a very high level of accumulation of a specialized gene product in mammalian cells.
12. The alpha-tropomyosin found in smooth muscle cells is different from the alpha-tropomyosin found in skeletal muscle cells. However, both are coded from the same gene. Explain how they become different from each other.
13. Describe an example of translational regulation.
14. Describe an example of a regulatory control that alters the stability of a messenger RNA.
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