$$\text{DNA} \xrightarrow{\text{transcription}} \text{RNA} \xrightarrow{\text{translation}} \text{Protein}$$

Question 1

Which of the following best describes the main difference between the lac operon and the trp operon in E. coli?

Accepted Answer

The lac operon is inducible, while the trp operon is repressible.

Question 2

In the absence of glucose and presence of lactose, what is the state of the lac operon in E. coli?

Accepted Answer

Transcription is on at a high level because CAP-cAMP is bound and the repressor is not bound.

Question 3

Which molecule acts as the inducer in the lac operon system?

Accepted Answer

Allolactose

Question 4

What is the role of the CAP-cAMP complex in the regulation of the lac operon?

Accepted Answer

It acts as an activator, enhancing RNA polymerase binding to the promoter.

Question 5

Which of the following equations correctly represents the central dogma of molecular biology?

Accepted Answer

$$	ext{DNA} \xrightarrow{	ext{transcription}} 	ext{RNA} \xrightarrow{	ext{translation}} 	ext{Protein}$$

Question 6

A mutation in the lacI gene results in a nonfunctional repressor protein. What is the expected outcome for lac operon expression?

Accepted Answer

The operon will be permanently on, regardless of lactose presence.

Question 7

Which of the following best explains why the trp operon is considered a repressible operon?

Accepted Answer

It is turned off when tryptophan is present, acting as a corepressor.

Question 8

Which of the following scenarios would result in the highest level of lac operon transcription?

Accepted Answer

Low glucose, high lactose

Question 9

In eukaryotes, which of the following is a key difference in gene regulation compared to prokaryotes?

Accepted Answer

Eukaryotes have one promoter per gene and use cis-acting elements and trans-acting factors.

Question 10

Which of the following best describes the function of alternative sigma factors in bacteria?

Accepted Answer

They allow RNA polymerase to recognize different sets of promoters under specific conditions.

Question 11

A yeast cell is growing in the presence of galactose but no glucose. Which proteins are active in promoting GAL gene expression?

Accepted Answer

Gal4 and Gal3

Question 12

Which of the following statements about the role of Mig1 in yeast gene regulation is correct?

Accepted Answer

Mig1 acts as a repressor in the presence of glucose by recruiting Tup1 to silence GAL gene transcription.

Question 13

Which of the following best describes the effect of an inducer molecule on a repressor protein in negative regulation?

Accepted Answer

The inducer binds to the repressor, causing it to release from the operator and allow transcription.

Question 14

Which of the following is a correct description of catabolism and anabolism?

Accepted Answer

Catabolism breaks down large molecules to release energy, while anabolism synthesizes large molecules using energy.

Question 15

A mutation in the Gal80 protein prevents it from binding to Gal4. What is the expected effect on GAL gene expression in yeast?

Accepted Answer

GAL genes will be constitutively expressed, regardless of galactose presence.

Question 16

Which of the following best explains why the order of genes in the trp operon matches the order of reactions in the tryptophan biosynthetic pathway?

Accepted Answer

It allows for coordinated regulation and efficient production of enzymes in the pathway.

Question 17

Which of the following is a key feature of eukaryotic transcription factors?

Accepted Answer

They have multiple functional domains, such as DNA-binding, dimerization, and activation/repression domains.

Question 18

Which of the following scenarios would result in the lowest level of lac operon transcription?

Accepted Answer

High glucose, low lactose

Question 19

Which of the following best describes the function of an enhancer in eukaryotic gene regulation?

Accepted Answer

A DNA sequence that increases transcription by facilitating the binding of transcription factors, even when located far from the gene.

Gene Regulation in Prokaryotes and Eukaryotes: The Lac, Trp, and Gal Systems CH 12 pt 3

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