Chapter_07_Solutions

Chapter_07_Solutions - Chapter 7 Control of Gene Expression...

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AN OVERVIEW OF GENE CONTROL DEFINITIONS 7–1 RNA transport control 7–2 Transcriptional control 7–3 mRNA degradation control 7–4 Translational control 7–5 RNA processing control TRUE/FALSE 7–6 False. Carrots can be grown from single carrot cells, and tadpoles can be got- ten by injecting differentiated frog nuclei into frog eggs. But carrots cannot be gotten from frog eggs no matter what. 7–7 False. Comparison of the patterns of expressed mRNAs underestimates the differences in the patterns of proteins produced in different specialized cell types because gene expression can be regulated at many steps after tran- scription. Differences in post-transcriptional regulation introduce addition- al differences into the protein profiles observed in different cell types. THOUGHT PROBLEMS 7–8 Each added phosphate alters the charge by one unit, but has relatively little effect on the molecular mass. As a consequence, proteins that differ only in the number of attached phosphates will appear at the same molecular mass, but at different isoelectric points, forming a set of horizontal spots, as shown for a few proteins in Figure 7–56. It is important to keep in mind that a horizontal array of spots does not prove that the proteins are related by A151 In This Chapter AN OVERVIEW OF A151 GENE CONTROL DNA-BINDING MOTIFS A153 IN GENE REGULATORY PROTEINS HOW GENETIC A159 SWITCHES WORK THE MOLECULAR A166 GENETIC MECHANISMS THAT CREATE SPECIALIZED CELL TYPES POST- A175 TRANSCRIPTIONAL CONTROLS Chapter 7 7 Control of Gene Expression acidic basic larger smaller Figure 7–56 Protein spots in a two- dimensional gel that might differ by the number of attached phosphates ( Answer 7–8 ). A few sets of horizontal spots that could be related by phosphorylation are boxed . Not all such sets of proteins are indicated.
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A152 Chapter 7: Control of Gene Expression phosphorylation; they could be different proteins with the same molecular mass and slightly different isoelectric points. Treatment of the proteins with a protein phosphatase before separation by gel electrophoresis could be used to resolve the issue. 7–9 Although it is true that cancer cells differ from their normal precursors, they typically differ in their expression of only relatively few genes (oncogenes and tumor suppressor genes). When the abundances of hundreds to thou- sands of mRNAs are compared, as they are in DNA microarray analysis, the patterns of mRNAs from the unaffected genes (the vast majority) allow a tumor to be definitively assigned to a particular tissue type. 7–10 A. The six types of regulation of gene expression are indicated at the appropri- ate points the diagram in Figure 7–57. B. Bacterial cells lack a nuclear membrane and other membrane-enclosed intracellular compartments. As a result, there is no RNA processing control or RNA transport and localization control.
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Chapter_07_Solutions - Chapter 7 Control of Gene Expression...

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