Question

In: Biology

The expression of genes is regulated in S. pneumoniae positive and negative regulators that respond to...

The expression of genes is regulated in S. pneumoniae positive and negative regulators that respond to signals from the environment.

a. How can the presence or absence of glucose change the expression of the lac operon?

b. How can the presence or absence of lactose change the expression of the lac operon?

c. How could the presence of absence of tryptophan change expression of the trp operon?

d. How could the presence of absence of chorismate change expression of the trp operon?

e. If a medium contained both chorismate and tryptophan, how would the expression of the trp operon change, if at all?

Solutions

Expert Solution

a. the presence of glucose reduces the concentration of cAMP and thereby, inactivates CRP/CAP. RNA polymerase cannot bind to the promoter and therefore, transcription is repressed.

when glucose is present in the medium, there is no need of lac operon. the lac operon is transcribed only in the presence of lactose and absence of glucose.

b. presence of lactose inactivates the repressor and turns ON the transcription from lac operon.

the absence of lactose turns OFF the transcription from the lac operon.

c. tryptophan acts as a co-repressor for tryptophan operon. when tryptophan is present, it activates the repressor and thereby, inactivates the trp operon. in its absence, Trp operon is transcribed.

d. chorismate acts as the precursor of tryptophan. since this is the main substrate, the presence of chorismate requires the tryptophan operon to be expressed.

e. chorismate is the substrate for tryptophan biosynthesis. the enzymes required for the synthesis of tryptophan from chorismate are encoded by tryptophan operon. when tryptophan is present in the medium, it would not allow the transcription to proceed. it represses the transcription.


Related Solutions

1Bacterial genes are regulated by riboswitches that respond to metabolites. Explain how riboswitches regulate gene expression...
1Bacterial genes are regulated by riboswitches that respond to metabolites. Explain how riboswitches regulate gene expression with two examples. 2 Describe the mechanism of regulation of gene expression by miRNA . List two pathways that are disrupted by increase in expression of certain miRNAS. Describe using a specific example,
Global regulators are proteins that can repress or activate the expression of large numbers of genes...
Global regulators are proteins that can repress or activate the expression of large numbers of genes in an organism. A recent report describes structural studies on the anti-repressor AbbA from the bacterium Bacillus subtilis [Tucker et aL, J. Mol. Biol. (2014)]. This protein has the ability to bind to a second protein, a global repressor named AbrB. These researchers first characterized their recombinant version of AbbA, a 65-residue protein prepared in E.coli cells. (Qa).During the isolation and purification of AbbA,...
Enzymes (or their production) are often regulated in a negative or positive way, depending on whether...
Enzymes (or their production) are often regulated in a negative or positive way, depending on whether they are related to anabolic (building) or catabolic (breaking down) reactions. Please describe, in your own words, why excess of products might inhibit enzymatic activity for anabolic reactions but why excess of reactants might stimulate enzymatic activity for catabolic reactions. This question is pretty complex, so take your time to develop your thoughts prior to typing your answer. The best answers should incorporate aspects...
At which of the following level(s) can gene expression be regulated in eukaryotes? Select one: a....
At which of the following level(s) can gene expression be regulated in eukaryotes? Select one: a. chromatin unfolding b. destruction of the mRNA c. rate of protein synthesis d. A and B e. A, B and C
The lac operon is regulated via positive and negative regulation. Explain how each mechanism works on...
The lac operon is regulated via positive and negative regulation. Explain how each mechanism works on this operon, and under which circumstances will the operon be turned on. Include the definition of an operon 2. What are the advantages to a microbe of having inducible enzymes? What is the function of toluene in the experiment where you induced enzyme function?
One of the assumptions underpinning economics is that rational, self-interested people respond to positive and negative...
One of the assumptions underpinning economics is that rational, self-interested people respond to positive and negative incentives to make decisions. Take your everyday lives. You have a negative incentive to speed in your car — costly ticket and higher cost insurance — but a positive incentive (reward) for staying under the speed limit. Suppose Maryland implemented a “three strikes and you’re out” law for extreme forms of polluting the Chesapeake Bay. A defendant with prior convictions for two offenses would...
Similar genes (homologs) are found in humans. Do you expect the expression of these genes to...
Similar genes (homologs) are found in humans. Do you expect the expression of these genes to be similar during human development? During cancer development?
Similar genes (homologs) are found in humans. Do you expect the expression of these genes to...
Similar genes (homologs) are found in humans. Do you expect the expression of these genes to be similar during human development? During cancer development?
What are positive and negative reinforcement? How are positive and negative reinforcement different? How are they...
What are positive and negative reinforcement? How are positive and negative reinforcement different? How are they similar? What is punishment?
The protein REST is a transcription factor that repressesthe expression of neuronal genes (genes only expressed...
The protein REST is a transcription factor that repressesthe expression of neuronal genes (genes only expressed in neurons). Predict whether REST would be found bound to the promoter of each gene in the designated tissue (think about whether they are expressed in each tissue). Write a “+” for located at the promoter and a “-“ for not located at the promoter. Brain Muscle Nav HK1 (hexokinase) RPL1 (ribosome protein) Kv
ADVERTISEMENT
ADVERTISEMENT
ADVERTISEMENT