ANSWERS TO CHAPTER EIGHT 1. Answer: b. Most prokaryotic genes are circular without a nucleus, although plasmids can exist. 2. Answer: a. The prokaryotic genes are usually negatively supercoiled, against the grain of the double helix. There are no histone or non-histone proteins involved. 3. Answer: a. The promotor sequence binds selectively to the RNA polymerase enzyme so that transcription can take place under the right circumstances. 4. Answer: b. These parts of a eukaryotic cell all contain individual DNA molecules. The eukaryotic cell does not have a nucleoid so there is no “nucleoid DNA” in a eukaryotic cell. 5. Answer: d. Luteinizing hormone is protein-based so it does not enter the nucleus. The others are steroid hormones that can enter the nucleus and can act as transcription factors. 6. Answer: a. The operator contains a sequence that can attach to an inhibitory protein in order to stop the production of the trp gene sequence. 7. Answer: d. Histone acetylation will decrease the binding activity of histone proteins to the DNA molecule so that transcription of the DNA sequence can happen. 8. Answer: a. In genomic printing, certain DNA segments get methylated so that DNA gets distinguished as being maternal or paternal in origin. Some genes, as a result, get expressed while others do not. 9. Answer: a. Most of the time, a mutation has no effect on the cell. Less commonly, some of the other effects can be seen, which are more dangerous complications for the cell. 10. Answer: c. A point mutation involves simply the substitution of one base for another. In sickle cell disease, glutamine is substituted for valine, leading to an abnormal hemoglobin protein.
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