MBG 3080 Lecture Notes - Lecture 5: Repressor, Plasmid, Chromosome
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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. |
For this question, focus on four parts:
I, the gene that produces the repressor protein;
P, the promoter region where RNA polymerase binds to initiate transcription;
O, the Operator site, where the repressor binds. When the repressor binds, it prevents transcription; and
ZYA, the three structural genes, all of which are required for the successful utilization of lactose as a food source.
In the left column of the table below, we indicate the genetic composition at the lac operon of particular strains of E. coli cells. A "+" (plus sign) following the letter indicates the wild-type allele (or normally functioning version of the gene). For I, P, and ZYA, a "-" (negative sign) following the letter indicates the mutant allele (or non-functional version of the gene). For the O allele, a "C" indicates the mutant or constitutive allele. It is not functional in that the repressor cannot bind, but it is functional in that transcription can still occur.
Given the conditions stated in each column, please indicate for each genotype whether lac mRNA is produced and at what level by typing in one of the following words in each cell in the table:
"Abundant"
"Minimal"
"None"
The completely wild-type genotype has already been filled in.
Cellular conditions: | |||
Genotype | Glucose present (low cAMP) and no lactose | Glucose present (low cAMP) and lactose present | No glucose (high cAMP) and lactose present |
I+ P+ O+ ZYA+ | None | Minimal | Abundant |
I- P+ O+ ZYA+ | |||
I+ P- O+ ZYA+ | |||
I+ P+ Oc ZYA+ | |||
I+ P+ O+ ZYA- |