Operon Regulation in E. coli

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Questions and Answers

What is the primary function of the operator in the lac operon?

To bind the repressor protein and prevent transcription (correct)
To bind lactose and induce gene expression
To bind RNA polymerase and initiate transcription
To bind the lacI gene and regulate its expression

What is the outcome of induction in the lac operon?

Inhibition of RNA polymerase
No change in gene expression
Repression of gene expression
Activation of gene expression (correct)

What is the key difference between negative and positive regulation?

Negative regulation is default off, while positive regulation is default on (correct)
Negative regulation is inducer-dependent, while positive regulation is repressor-dependent
Negative regulation is specific to the lac operon, while positive regulation is specific to the trp operon
Negative regulation is default on, while positive regulation is default off

Which of the following is an example of positive regulation?

Maltose operon (D) Signup and view all the answers

What is the role of the lacI gene in the lac operon?

To encode the lac repressor protein (D) Signup and view all the answers

What is the primary function of the promoter in the lac operon?

To bind RNA polymerase and initiate transcription (C) Signup and view all the answers

What is the primary function of cis-elements in gene regulation?

To bind to trans-acting factors to regulate gene expression (D) Signup and view all the answers

Which of the following is a mechanism of post-transcriptional regulation?

Regulation of mRNA stability (B) Signup and view all the answers

What is the primary outcome of epigenetic regulation?

Modification of chromatin structure to affect gene accessibility (A) Signup and view all the answers

What is the role of coactivators in transcriptional regulation?

To enhance activator function by binding to trans-acting factors (C) Signup and view all the answers

Which of the following is a mechanism of transcriptional regulation?

Recruitment of RNA polymerase to promoter regions (A) Signup and view all the answers

What is the primary function of trans-acting factors in gene regulation?

To bind to cis-elements to regulate gene expression (D) Signup and view all the answers

What is the reason behind the ribosomes' preference for a particular reading frame?

The difference in the initiation of translation (D) Signup and view all the answers

What is the mechanism by which the p32 protein regulates its own translation?

By binding to its own mRNA (A) Signup and view all the answers

What is the function of the ribosomal proteins in the regulation of ribosome synthesis?

To regulate the ratio of ribosomal proteins (D) Signup and view all the answers

How do ribosomal proteins recognize their own mRNA?

Through an interaction with the rRNA (B) Signup and view all the answers

What is the consequence of having excess ribosomal proteins?

The ribosomal proteins bind to their own mRNA (B) Signup and view all the answers

What is the mechanism of regulation of ribosomal protein synthesis?

Autoregulation (A) Signup and view all the answers

What is the purpose of grouping several genes into a polycistronic operon?

To co-regulate the expression of all the genes (C) Signup and view all the answers

What is the outcome of the interaction between the protein ribosomal S8 and the 16S rRNA?

The protein S8 blocks a region of the 16S rRNA, making it inaccessible (B) Signup and view all the answers

Why do some phages require a specific order of protein appearance during their infection mechanism?

To allow the translation of the mRNA to occur in a specific order (C) Signup and view all the answers

What is the function of the Shine-Dalgarno sequence in mRNA translation?

To recruit ribosomes for translation initiation (B) Signup and view all the answers

What is the role of the secondary structure of the mRNA in protein translation?

It inhibits the translation of the mRNA by masking the Shine Dalgarno box (A) Signup and view all the answers

Why might some proteins in an operon need to be translated in greater quantities than others?

Because of the stoichiometry of the protein complex (B) Signup and view all the answers

What is the significance of the height of the peaks in the diagram shown?

It represents the number of ribosomes translating each region of the mRNA (D) Signup and view all the answers

What is the outcome of the binding of the protein ribosomal S8 to the 16S rRNA in the ribosome?

The protein S8 blocks a region of the 16S rRNA, making it inaccessible (A) Signup and view all the answers

What might be the consequence of translating all the genes in an operon in equal quantities?

Insufficient amounts of some proteins would be synthesized (B) Signup and view all the answers

How do successive ribosomes translate previously masked mRNA sequences?

By breaking the secondary structure of the mRNA (C) Signup and view all the answers

What is the purpose of the secondary structure of the mRNA in regulating protein translation?

To inhibit the translation of the mRNA by masking the Shine Dalgarno box (B) Signup and view all the answers

What is the purpose of adjusting the translation of some genes in an operon?

To adjust the stoichiometry of the protein complex (D) Signup and view all the answers

Why do some mRNAs form a curved structure to regulate protein translation?

To inhibit the translation of the mRNA by masking the Shine Dalgarno box (D) Signup and view all the answers

What is the outcome of the translation of previously masked mRNA sequences by successive ribosomes?

The protein is translated in a specific order (A) Signup and view all the answers

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