Bio Final Lecture 36 – Flashcards
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At which of the following stages does transcriptional control occur?
a b c
DNA ——> mRNA ——> protein ——> activated protein
a
b
c
All of the answers represents transcription.
None of the answers represents transcription
answer
a
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Of the three modes of gene regulation shown in Figure 18.1, which is the fastest in response time?
Transcriptional control
Post-translational control
Translational control
All three are equally fast.
answer
Post-translational control
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Which of the following levels of gene expression control allows a cell to conserve the most resources?
post-translational control
pre-RNA splicing control
transcriptional control
translational control
answer
transcriptional control
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What is the role of lactose in regulating lac operon expression?
It induces transcription by binding directly to the promoter and attracting RNA Polymerase.
It represses transcription by binding to the repressor.
It induces translation by binding to the repressor and removing it from the mRNA.
It induces transcription by binding to the repressor and causing its release from the operator.
answer
It induces transcription by binding to the repressor and causing its release from the operator.
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The lac repressor protein binds to the operator when it is ______.
not bound to lactose
bound to glucose
not bound to glucose
bound to lactose
bound to arabinose
answer
not bound to lactose
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Bacterial and eukaryotic cells primarily control gene expression at the level of transcription. If instead cells exerted control of gene expression primarily at the post-translational level, what would be different?
Genes would no longer be transcribed.
The ability to rapidly respond to environmental change would be reduced.
Cells would expend significantly more energy.
Translation of mRNA into protein would not occur.
answer
Cells would expend significantly more energy.
question
Which of the following proteins is/are likely to be expressed constitutively in E. coli cells? Choose all that apply.
A glycolytic enzyme
Thiogalactoside transacetylase
Beta-galactosidase
Lac repressor
Lactose permease
RNA polymerase
answer
A glycolytic enzyme
Lac repressor
RNA polymerase
question
Of the three modes of gene regulation shown in Figure 18.1, which is the most efficient in resource use?
Translational control.
Transcriptional control
Post-translational control
All three are equally efficient.
answer
Transcriptional control
question
An E. coli cell without a functional lacI gene is expected to _____.
never produce β-galactosidase
be unable to transport lactose into the cell
always produce β-galactosidase
be unable to metabolize lactose within the cell
answer
always produce β-galactosidase
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The operon model of the regulation of gene expression in bacteria was proposed by _____.
Watson and Crick
Franklin
Darwin
Jacob and Monod
Mendel
answer
Jacob and Monod
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Which of these is NOT a component of the lac operon?
promoter only
regulatory gene only
operator only
promoter and operator
answer
regulatory gene only
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Regulatory proteins bind to _____.
the operator
the lactose-utilization genes
the regulatory gene
RNA polymerase
transcription factors
answer
the operator
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In the presence of a regulatory protein the lac operon is _____.
transcribed
not transcribed
transcribed at a faster than usual rate
is turned on
either transcribed or not transcribed
answer
not transcribed
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transcriptional control
answer
the cell could avoid making the mRNAs for particular enzymes
regulatory proteins affect RNA polymerases ability to bind to promoter and initiate transcription
most efficient, bc earliest form of regulation
DNA -X-> mRNA ---> protein ---> activated protein
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translational control
answer
if the mRNA for an enzyme has been made, the cell could prevent the mRNA from being translated into protein
regulatory molecules alter the length of time an mRNA survives, or affect translation initiation or elongation
allows for rapid changes in amount of proteins bc mRNAs are present and available
DNA ---> mRNA -X-> protein ---> activated protein
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post-translational control
answer
regulating the step in which many proteins have to be activated by chemical modifications, such as the addition of a phosphate group
most rapid response bc only one step is needed to activate existing proteins
DNA ---> mRNA ---> protein -X-> activated protein
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constitutively
answer
these genes are transcribed at all times
EX. gene for glycolysis
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lactose
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disaccharide made from 1 glucose and 1 galactose
used when glucose is not present
must be transported into cell, broken down by B-galactosidease, then monomers enter glycolytic pathway
an inducer for B-galactosidase and galactoside permease
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B-galactosidase
answer
breaks down lactose into glucose and galactose
produced in high amounts when lactose is present in high amounts
if glucose and lactose present in high amounts, not needed
coded for by lacZ
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to find mutant E.coli that could not metabolize lactose
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exposed E.coli to mutagens (X-rays, UV light, or chemicals that damage DNA)
screened cells for defects in lactose metabolism
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replica plating
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mutagenized bacteria spread on master plate contain growth medium (glucose and lactose)
a block covered in sterilized velvet is pressed onto master plate so some cells get transferred
velvet is pressed onto replica plate that has different medium (only lactose) and colonies grow
compare replica plate to master plate: colonies on master plate but not on replica plate are the colonies that can't metabolize glucose
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3 types of mutants
answer
1. unable to cleave lactose even with lactose present in cell: must have dysfunctional B-galactosidase gene (lacZ-)
2. membrane proteins unable to transport lactose into cell: must have dysfunctional galactoside permease gene (lacY-)
3. B-galactosidase and galactoside permease present even when lactose wasn't: must have dysfunctional regulatory gene (lacI-) - CONSTITUTIVE MUTANT
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constitutive mutant
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produces a product at all times instead of only when it needs it
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lacI
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produces regulatory/repressor protein that doesn't allow for transcription of lacZ and lacY unless lactose is present by binding to operator
uses negative control
expressed constitutively
its protein undergoes post translational control
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negative control
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occurs when a regulatory protein called a repressor binds to DNA and shuts down transcription
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postive control
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occurs when a regulatory protein called an activator binds to DNA and triggers transcription
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inducer
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small molecule that triggers transcription of a specific gene
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lac operon
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a set of coordinately regulated bacterial genes that are transcribed together into one mRNA that produced proteins to metabolize lactose
lacZ, lacY, and lacA are adjacent and transcribed into 1 mRNA initiated from the promoter
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galactoside permease
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protein that allows entry of lactose into cell
coded for by lacY
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transacetylase
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catalyzes reactions that allow certain types of sugars to be exported from the cell when they are to abundant and could harm the cell
coded for by lacA
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allosteric regulation
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a small molecule (allolactose from lactose) binds to protein (repressor) and makes it fall off operator, so RNA polymerase can now bind to promoter and transcribe lac operon
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glucose does inducer exclusion
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inhibits transport activity of galactoside permease
lactose does not accumulate in cell, and repressor stays activated
question
Which of the following proteins is likely to be constitutively expressed in E. coli?
Choose all that apply.
Ribosomal proteins
Enzymes for using glucose as a food source
Enzymes for using lactose as a food source
RNA polymerases
answer
Ribosomal proteins
Enzymes for using glucose as a food source
RNA polymerases
