BIOCHEM 275 Lecture Notes - Lecture 31: Lac Repressor, Allolactose, Lac Operon
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QUESTION 1
In the bacterial lac repressor, which of these occurs: (select all that apply)
(a)In the presence of glucose and the absence of lactose, the repressor is actively produced. | ||
(b)The lac operon can be hyper-induced in the presence of low glucose by the 'cAMP binding protein' (CAMP). | ||
(c)In the presence of lactose and the absence of glucose the lac operon is repressed. | ||
(d)Allolactose is a byproduct of β-galactosidase, indicating high lactose when it builds up. |
1.5 points
QUESTION 2
In eukaryotes the enhancer elements can be quite a distance upstream or downstream from the promoter, and transcriptional regulation is helped by protein:protein interactions.
True
False
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QUESTION 3
The prokaryotic promoter contains a TATA box that is at -10bp upstream from the transcriptional start site.
True
False
1.5 points
QUESTION 4
During the addition of the poly A tail which of these occurs:(select all that apply)
(a)The transcript is synthesized beyond the poly A site (AAUAAA). | ||
(b)The mRNA contains a 5â cap. | ||
(c)The transcript is cleaved 35nt downstream from the poly A site. | ||
(d)An enzyme complex containing an exonuclease and polyadenylate polymerase cleaves nearby the AAUAA site. | ||
(e)100-300 Aâs are added to the 5â end. |
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. |