Question 1

Which of the following best describes the function of the lac operon in E. coli when lactose is present and glucose is absent?

Accepted Answer

The Lacl repressor is inactivated, CAP-cAMP complex binds to the promoter, and transcription of the lac operon is induced.

Question 2

A mutation in the operator region of the lac operon prevents the Lacl repressor from binding. What is the expected phenotype?

Accepted Answer

Transcription of the lac operon is constitutive, occurring even in the absence of lactose.

Question 3

Which sequence is recognized as the consensus for the TATA box in eukaryotic promoters?

Accepted Answer

$TATAAA$

Question 4

In eukaryotes, which element is typically located far from the gene it regulates and can loop around to interact with the promoter?

Accepted Answer

Enhancer

Question 5

Which of the following is TRUE regarding the Shine-Dalgarno sequence?

Accepted Answer

It is located approximately 8 base pairs upstream of the start codon in prokaryotes.

Question 6

Which process is responsible for removing non-coding regions from pre-mRNA in eukaryotes?

Accepted Answer

Intron splicing

Question 7

A researcher adds a wild-type operator region on an F plasmid to a bacterial cell with a defective operator ($O^c$) in its chromosome. Will this rescue the mutant phenotype? Why?

Accepted Answer

No, the operator must be adjacent to the lacZ gene to regulate its expression.

Question 8

Which of the following is a function of the poly(A) tail added to eukaryotic mRNA?

Accepted Answer

Stabilizes mRNA and facilitates export from the nucleus

Question 9

Given the DNA sequence: 5'-TTATGACCACCATGGCTTAA-3', what is the amino acid sequence encoded?

Accepted Answer

Met-Asp-His-His-Gly-Leu

Question 10

Which of the following statements about combinatorial control in eukaryotic gene regulation is correct?

Accepted Answer

Multiple transcription factors bind to various cis-acting elements to regulate gene expression.

Question 11

Which of the following is a cis-acting element in eukaryotic gene regulation?

Accepted Answer

Enhancer

Question 12

What is the role of the Kozak sequence in eukaryotic translation?

Accepted Answer

It helps ribosomes recognize the start codon for translation initiation.

Question 13

Which of the following best explains why glucose inhibits transcription of the lac operon?

Accepted Answer

Glucose decreases cAMP levels, reducing CAP-cAMP complex formation and thus transcription.

Question 14

Which of the following is NOT a stage at which gene regulation can occur in eukaryotes?

Accepted Answer

Gene duplication

Question 15

Which experiment would best test the function of a distal enhancer in tissue-specific gene expression?

Accepted Answer

Delete the enhancer region and observe changes in gene expression in specific tissues.

Question 16

Which of the following is TRUE about alternative splicing?

Accepted Answer

It allows a single gene to produce multiple protein isoforms.

Question 17

Which of the following best describes a consensus sequence?

Accepted Answer

A sequence that represents the most common nucleotides at each position among related sequences.

Question 18

Which of the following is a trans-acting element in gene regulation?

Accepted Answer

Transcription factor

Question 19

A mutation in the polyadenylation signal ($AAUAAA$) of a gene would most likely result in which of the following?

Accepted Answer

Unstable mRNA and reduced export from the nucleus

Gene Regulation in Prokaryotes and Eukaryotes: Mechanisms and Elements - Nov 7

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