BIOL308 Study Guide - Final Guide: Northern Blot, Structural Motif, Glutamine
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A transcription factor G can act as either a repressor or an activator of operon M, depending on its conformational state.
In one conformational state, transcription factor G binds site 1 in the promoter of operon M. When bound to site 1, it is an activator of operon M transcription. Factor G cannot bind to site 1 if ligand X is bound to it.
When factor G binds to ligand X, factor G undergoes a conformational change such that it now binds site 2 in the promoter and represses operon M. Because of the way in which it acts, ligand X would be called a(n) ____.
Imagine that there is a mutation in the gene that encodes transcription factor G such that operon M is always transcribed.
Which of these mutations in the gene that encodes transcription factor G is consistent with that outcome?
More than one answer may be correct.
'The mutation changes transcription factor G such that it ___'
| cannot bind site 1 |
| cannot bind site 2 |
| cannot bind to ligand X |
| cannot dissociate from ligand X once it has bound Continuing with the system in Questions 4 and 5, imagine that you are now analyzing mutations in the promoter of operon M. If site 1 is mutated such that factor G cannot bind, operon M will never be ____
|
1. What is the term when the product of a biochemical pathway inhibits the activity of the first enzyme of a pathway?
| feedback inhibition. | ||
| activator inhibition. | ||
| diffusional regulation. | ||
| enzyme activation. |
2. Through control of gene expression, prokaryotes respond to changing __________ conditions.
| internal | ||
| protein | ||
| environmental | ||
| genetic |
3. A protein that negatively regulates transcription by binding to the operator is known as the
| operon | ||
| repressor | ||
| activator | ||
| inducer |
4. During attenutation, when tryptophan levels are high, the ________ stem-loop forms and transcription ________ the trpL gene.
| 1-2, ends just past | ||
| 3-4, ends just past | ||
| 1-2, continues beyond | ||
| 3-4, continues beyond |
5. The process of turning on the expression of a gene in response to a substance in the environment is called:
| constituation. | ||
| repression. | ||
| induction. | ||
| catabolism. |
6. What is a function of some specific transcription factors?
| to bind to the promoter region of the gene to facilitate the proper alignment of the RNA polymerase | ||
| to bind to the centromere to induce meiosis | ||
| to bind to enhancer regions to help regulate gene transcription | ||
| to bind to the operator to recruit sigma factor |
7. How does exposing an E.coli cell to glucose affect the regulation of the lac operon via CAP?
| cAMP binds to CAP and transcription is increased. | ||
| cAMP binds to CAP and transcription is decreased. | ||
| cAMP does not bind to CAP and transcription is increased. | ||
| cAMP does not bind to CAP and transcription is decreased. |
8. The lac repressor protein works when mutations in the repressor gene and structural genes are:
| in cis or in trans. | ||
| in trans only. | ||
| in cis only. | ||
| in both prokaryotes and eukaryotes. |
QUESTION 10
If you can drink milk as an adult, it means that you have inherited a mutation in the promoter of your lactase gene (the gene that encodes the enzyme you need to break down lactose). Predict the effect of this mutation:
| The mutation changes the number of domains in the enzyme, which makes it work more efficiently | ||
| The mutation changes the amino acid sequence of the lactase protein | ||
| The mutation increases the number of copies of the lactase gene that will be found in your genome | ||
| The mutation changes whether the lactase sequence is found in an intron or exon | ||
| The mutation affects the expression of the lactase gene |
1.2 points
QUESTION 11
A competitive inhibitor is decreasing the activity of an enzyme. Predict the effect of adding more substrate to the reaction.
| The substrate will increase the reaction rate by binding to the allosteric site | ||
| The substrate will increase the reaction rate by competing with the inhibitor for the active site | ||
| The reaction rate will not change unless the inhibitor can be removed | ||
| The enzyme adjusts its shape so that the substrate, but NOT the competitive inhibitor, can bind | ||
| The substrate will bind to the competitive inhibitor and block its ability to bind to the enzyme |
1.2 points
QUESTION 12
What determines where in the genome a transcription regulator will bind?
| Transcription regulators bind to the 5' UTR region of a gene | ||
| Regulators bind via complementary base-pairing to certain DNA molecules | ||
| Covalent bonds form between the transcription regulator and the atoms of the DNA backbone | ||
| Every eukaryotic gene has a different transcription regulator that will bind to the 5' end of the gene | ||
| Transcription regulators bind to specific DNA sequences via multiple weak non-covalent interactions |
1.2 points
QUESTION 13
What is the basic premise of cell theory?
| DNA -> RNA -> protein | ||
| All cells arise from pre-existing cells | ||
| DNA provides the complete instructions to create a cell | ||
| The identity of a cell is determined through gene expression patterns | ||
| All cells contain the same four basic macromolecules |
1.2 points
QUESTION 14
What is the benefit of using BOTH the lac activator and the lac repressor to control gene expression?
| Using both an activator and repressor enables cells to more accurately determine the amount of lactose available in the environment | ||
| Enzymes to digest lactose are only made when energy is low and lactose is available | ||
| The activator can override the inhibition of the lac operon by the repressor | ||
| The repressor can control the enhancer, while the activator can control the promoter | ||
| When neither the lac activator or repressor is present, expression of the lac operon is too high |
1.2 points
QUESTION 15
What is the histone code used for?
| Phosphorylation and acetylation of DNA affect its ability to be compacted | ||
| Changes to the sequence of DNA change whether DNA will wrap around histone proteins | ||
| Covalent modifications of histones affect the ability of the transcription initiation complex to form | ||
| Histones provide the codon sequences needed for translation to occur | ||
| The histone code affects which amino acids will get added to a polypeptide |