Q: Which equation best represents the feedback inhibition mechanism in the tryptophan biosynthesis pathway?

$$E_1 + $$Trp \rightarrow $$E_1$$^* \rightarrow \text{decreased activity}$$

Question 1

Which of the following best explains why genetically identical cells in a multicellular organism can perform different functions?

Accepted Answer

Gene regulation allows different sets of genes to be expressed in different cells.

Question 2

In E. coli, diauxic growth occurs when two carbon sources are present. Which statement best describes the two phases of diauxic growth?

Accepted Answer

The more efficient carbon source (e.g., glucose) is metabolized first, then after exhaustion, the second source is used.

Question 3

Which equation best represents the feedback inhibition mechanism in the tryptophan biosynthesis pathway?

Accepted Answer

$$E_1 + $$Trp ightarrow $$E_1$$^* ightarrow 	ext{decreased activity}$$

Question 4

Which of the following is TRUE regarding the lac operon in E. coli?

Accepted Answer

The lac operon is inducible and is activated in the presence of lactose and cAMP.

Question 5

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

Accepted Answer

It enhances RNA polymerase binding to the promoter, increasing transcription.

Question 6

Which of the following best describes the difference between inducible and repressible operons?

Accepted Answer

Inducible operons are OFF until an inducer is present; repressible operons are ON until a corepressor is present.

Question 7

Which of the following modifications is most likely to increase gene expression in eukaryotes?

Accepted Answer

Histone acetylation by HATs, neutralizing lysine's positive charge

Question 8

A mouse with a yellow coat and obesity phenotype is born to a mother whose diet lacked methyl-donating compounds. What is the molecular basis for this phenotype?

Accepted Answer

Hypomethylation of the agouti gene leads to its overexpression.

Question 9

Which of the following is an example of epigenetic inheritance?

Accepted Answer

DNA methylation patterns affecting gene expression and inherited across generations

Question 10

In C. elegans, starvation induces small RNAs that are inherited for at least three generations. What is the effect of these small RNAs on the offspring?

Accepted Answer

They regulate gene expression, resulting in phenotypes resembling starved ancestors.

Question 11

Which of the following layers of eukaryotic gene regulation involves the removal of introns from pre-mRNA?

Accepted Answer

RNA processing

Question 12

Which equation best represents the effect of histone acetylation on chromatin structure?

Accepted Answer

$$	ext{Histone} + 	ext{Acetyl group} ightarrow 	ext{Neutralized charge} ightarrow 	ext{Loosened chromatin}$$

Question 13

Which of the following is a function of miRNAs in eukaryotic cells?

Accepted Answer

They block translation by binding to complementary mRNA sequences.

Question 14

A mutation in the 3' untranslated region (UTR) of an mRNA reduces its stability. What is the most likely consequence?

Accepted Answer

Decreased protein production due to rapid mRNA degradation.

Question 15

Which of the following statements about RNA editing by ADAR is correct?

Accepted Answer

ADAR converts adenosine to inosine, which is read as guanosine during translation.

Question 16

Which of the following best describes the role of enhancers in eukaryotic gene regulation?

Accepted Answer

Enhancers are DNA sequences that increase transcription of associated genes, often acting from a distance.

Question 17

Which of the following is a real-world example of positive gene regulation?

Accepted Answer

Binding of the cAMP-CRP complex to the lac operon promoter, enhancing transcription.

Question 18

Which of the following best explains why the lag phase occurs during diauxic growth in E. coli?

Accepted Answer

Cells are adapting to the depletion of the first carbon source and activating genes for the second source.

Question 19

Which of the following is NOT a layer of eukaryotic gene regulation?

Accepted Answer

Operon organization

Gene Regulation in Prokaryotes and Eukaryotes: Operons, Epigenetics, and Transcriptional Control

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