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Unit 8 SMG
EXAM 3
| Question | Answer |
|---|---|
| Mechanisms for controlling enzyme activity include all of the following EXCEPT | addition of short sections of new amino acid sequence. |
| The major site of protein binding in DNA is the major groove. Why is this a good site for binding? | Because the major groove is wider, it is more accessible to binding proteins. |
| ________ pathways typically utilize ________ proteins that stimulate binding of RNA polymerase to DNA. | Catabolic; activator |
| ________ pathways typically rely on ________ proteins to inhibit mRNA synthesis. | Anabolic; repressor |
| In negative control of transcription by the lac operon, how does the presence of an inducer affect transcription? | The inducer prevents the repressor from binding to the operator. |
| What occurs when an inducer is added to an environment containing an organism with a metabolic pathway controlled by a repressor? | The inducer combines with the repressor and inactivates the repressor. |
| In certain circumstances, a single regulatory protein controls multiple operons. This situation would be called a(n) __________. | regulon |
| The promoters of positively controlled operons require activator proteins because | the promoters bind RNA polymerase weakly and utilize activator proteins to help RNA polymerase recognize the promoter. |
| Cyclic AMP is synthesized from ATP by an enzyme called ________ which is involved in ________. | adenylate cyclase / catabolite repression |
| Bacteria can regulate gene expression due to changes in the environment. How are these changes communicated to the cell? | A sensor kinase on the cell membrane recognizes the change and transfers the information to a response regulator in the cytoplasm. |
| Why are two-component regulatory systems particularly useful for controlling gene expression in response to environmental signals? | Phosphorylation is a permanent change so genes are always turned on after signal. |
| Quorum sensing relies upon a large cell population which then turns on transcription. | True |
| A change in the nucleotide sequence of DNA that is passed on to daughter cells is referred to as __________. | a mutation |
| There are several different types of mutations possible in the base sequence of DNA. If a GGC (glycine) codon were changed to UGC (cysteine), it would be termed a __________. | missense mutation |
| A single base substitution happens to cause a nonsense mutation early in the gene for a protein. What will be the result? | The protein will be truncated so much that it is unlikely to function normally. |
| Frameshift mutations can be very severe. What is one reason why they are often so serious? | When a frameshift mutation occurs, it causes changes in many bases downstream and can affect many of the amino acids in the protein. |
| The SOS system repairs DNA that has gaps, breaks, and other lesions by | using specialized DNA polymerases that will synthesize a new DNA strand even if there is not a normal complementary DNA strand to act as a template. |
| Chemical mutagens, UV radiation, and ionizing radiation all increase mutation rates, but they have different mechanisms. Which type of mutagen would be best suited for creating large deletions and rearrangements within a genome? | ionizing radiation |
| The F (fertility) plasmid contains a set of genes that encode for the ________ proteins that are essential in conjugative transfer of DNA. | pili |
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