Question 1

Which of the following best describes the mechanism by which eukaryotic transcription factors regulate gene expression?

Accepted Answer

They bind to specific DNA sequences to either facilitate or inhibit the recruitment of RNA polymerase to the promoter.

Answer

They bind directly to the poly-A tail of mRNA to increase the half-life of the transcript in the cytoplasm.

Answer

They act as enzymes that catalyze the formation of phosphodiester bonds between ribonucleotides during elongation.

Answer

They remove introns from the pre-mRNA transcript to ensure the correct protein sequence is translated.

Question 2

In eukaryotic cells, many transcription factors function as activators. How do these activators typically increase the rate of gene expression?

Accepted Answer

By binding to enhancer regions and interacting with mediator proteins to loop the DNA, bringing the activator into contact with the promoter complex.

Answer

By binding to metabolic precursors to increase the concentration of available uracil in the nucleus.

Answer

By altering the primary structure of the RNA polymerase protein to increase its affinity for all DNA sequences.

Answer

By binding to stop codons on the DNA template to ensure that transcription does not terminate prematurely.

Question 3

Which of the following describes how a repressor protein prevents gene expression in an operon or eukaryotic gene system?

Accepted Answer

The repressor binds to a specific DNA sequence, such as an operator, physically blocking RNA polymerase from transcribing the gene.

Answer

The repressor degrades the RNA polymerase protein before it can reach the nucleus.

Answer

The repressor adds a methyl group to the phosphate backbone of the mRNA to prevent translation.

Answer

The repressor binds to the ribosome to prevent the attachment of the mRNA transcript.

Question 4

Which of the following describes the role of general (basal) transcription factors in eukaryotic gene expression?

Accepted Answer

They bind to the TATA box within the promoter to help position RNA polymerase II correctly for the initiation of transcription.

Answer

They bind to the protein-coding regions of the gene to signal the end of transcription.

Answer

They catalyze the addition of a 5' cap to the emerging mRNA transcript during elongation.

Answer

They function as methyltransferases that add methyl groups to cytosine bases to silence gene activity.

Question 5

Research indicates that some transcription factors function by recruiting histone acetyltransferase (HAT) enzymes to specific gene loci. How does this recruitment facilitate gene expression?

Accepted Answer

The addition of acetyl groups to histone tails reduces their positive charge, loosening the chromatin structure to make DNA more accessible to RNA polymerase.

Answer

The addition of acetyl groups increases the hydrophobicity of the DNA, causing it to separate from the aqueous environment of the nucleus.

Answer

The acetyl groups serve as a chemical signal that triggers the immediate degradation of repressors present in the nucleoplasm.

Answer

Acetylation triggers the conversion of the DNA double helix from a B-form into a Z-form, which allows for faster elongation by RNA polymerase.

Question 6

Which of the following describes how a single eukaryotic transcriptional activator can coordinate the expression of multiple genes located on different chromosomes?

Accepted Answer

The activator recognizes and binds to a specific, identical regulatory DNA sequence associated with each of the dispersed genes.

Answer

The activator converts the different genes into a single polycistronic mRNA molecule through trans-splicing.

Answer

The activator facilitates the physical movement of all the genes to a single chromosome for simultaneous transcription.

Answer

The activator functions as a specialized tRNA that carries the same amino acid to multiple different ribosomes.

Question 7

In the regulation of gene expression, how do certain transcription factors utilize the process of signal transduction to initiate transcription?

Accepted Answer

Extracellular signaling molecules lead to the activation of intracellular kinases, which phosphorylate and activate specific transcription factors that then enter the nucleus to bind to DNA.

Answer

The signal molecules act as ligands that bind directly to the TATA box, causing a conformational change in the DNA double helix.

Answer

Extracellular signals cause transcription factors to be exported from the nucleus to the cytoplasm where they can bind to ribosomes and increase translation.

Answer

Signal transduction pathways lead to the destruction of RNA polymerase, allowing the cell to switch to using DNA polymerase for RNA synthesis.

Question 8

Which of the following describes the functional difference between the 'DNA-binding domain' and the 'activation domain' of a eukaryotic transcription factor?

Accepted Answer

The DNA-binding domain recognizes specific nucleotide sequences, while the activation domain interacts with other proteins like RNA polymerase or mediator to increase transcription.

Answer

The DNA-binding domain identifies introns for removal, while the activation domain adds the 3' poly-A tail to the transcript.

Answer

The DNA-binding domain attaches to the ribosome, while the activation domain unwinds the DNA double helix during elongation.

Answer

The DNA-binding domain synthesizes the mRNA transcript, while the activation domain binds to the promoter's TATA box.

Question 9

Which of the following describes the mechanism by which a transcription factor acts as a 'silencer' to regulate gene expression?

Accepted Answer

The transcription factor binds to a specific DNA sequence and recruits histone deacetylases (HDACs), leading to a more condensed chromatin structure that prevents transcription.

Answer

The transcription factor binds to the tRNA molecules, preventing them from delivering amino acids to the growing polypeptide chain.

Answer

The transcription factor acts as a nuclease that cleaves the promoter sequence, permanently disabling the gene's ability to be expressed.

Answer

The transcription factor binds to the mRNA transcript in the cytoplasm and prevents it from associating with the small ribosomal subunit.

Question 10

Which of the following describes the role of 'combinatorial control' in the regulation of eukaryotic gene expression by transcription factors?

Accepted Answer

The specific combination of multiple different transcription factors binding to several enhancer elements determines whether a gene is transcribed in a particular cell type.

Answer

Transcription factors must bind in a specific numerical order (1, 2, 3...) to the DNA template to allow RNA polymerase to move past the first intron.

Answer

A single transcription factor is capable of binding to every gene in the genome simultaneously to ensure uniform protein levels.

Answer

The cell uses a different transcription factor for every single nucleotide in the gene sequence to ensure high fidelity during transcription.

Related quizzes

Related quizzes