AP Ch Quiz Ch 16 Gene Regulation

1.

Which statement is NOT correct about the lac operon?

A.

It regulates the production of a series of five enzymes.
B.

It is normally turned off if glucose is present.
C.

Lactose binds to the repressor protein and inactivates it.
D.

It is an inducible system.
E.

The structural genes make products that allow lactose metabolism.

Correct Answer
A. It regulates the production of a series of five enzymes.

Explanation
The lac operon is a regulatory system found in bacteria that controls the metabolism of lactose. It consists of three structural genes that encode enzymes involved in lactose metabolism. When lactose is present, it binds to the repressor protein, causing it to detach from the operator region of the operon. This allows RNA polymerase to transcribe the structural genes, resulting in the production of the enzymes. Therefore, the statement "It regulates the production of a series of five enzymes" is not correct because the lac operon regulates the production of three enzymes, not five.

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2.

Which statement is NOT correct about the trp operon?

A.

The structural genes make products that act in a metabolic pathway to produce tryptophan.
B.

It is normally turned off if tryptophan is present.
C.

Tryptophan acts as the corepressor.
D.

The regulator gene product is inactive by itself.
E.

Tryptophan binds to the repressor protein and inactivates it.

Correct Answer
E. TryptopHan binds to the repressor protein and inactivates it.

Explanation
The trp operon is normally turned on if tryptophan is present, not turned off. Tryptophan acts as the corepressor, not as the activator. The regulator gene product is active by itself, not inactive. Therefore, the statement "Tryptophan binds to the repressor protein and inactivates it" is NOT correct about the trp operon.

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3.

Which level of primary control in eukaryotic gene activity involves the life span of the mRNA molecule and the ability of the mRNA to bind to ribosomes?

A.

Feedback control
B.

Translational control
C.

Transcriptional control
D.

Posttranscriptional control
E.

Posttranslational control

Correct Answer
B. Translational control

Explanation
Translational control refers to the regulation of gene expression at the level of translation, where the mRNA molecule is translated into a protein by ribosomes. This level of control involves the regulation of the life span of the mRNA molecule and its ability to bind to ribosomes. It determines the rate at which proteins are synthesized from the mRNA molecules, thus influencing the overall gene activity.

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4.

Which level of primary control in eukaryotic gene activity involves processing early RNA transcripts to mRNA and control of the rate at which mRNA leaves the nucleus?

A.

Feedback control
B.

Translational control
C.

Transcriptional control
D.

Posttranscriptional control
E.

Posttranslational control

Correct Answer
D. Posttranscriptional control

Explanation
Posttranscriptional control involves the processing of early RNA transcripts to mRNA and the regulation of the rate at which mRNA leaves the nucleus. This level of control occurs after transcription has taken place, but before translation occurs. It includes processes such as RNA splicing, capping, polyadenylation, and RNA editing, which modify the mRNA molecule. Additionally, posttranscriptional control can also involve the regulation of mRNA stability and localization within the cell. Overall, posttranscriptional control plays a crucial role in determining the abundance, stability, and localization of mRNA, thereby influencing gene expression in eukaryotic cells.

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5.

Which level of primary control in eukaryotic gene activity involves changes in the polypeptide chain before it becomes functional?

A.

Feedback control
B.

Translational control
C.

Transcriptional control
D.

Posttranscriptional control
E.

Posttranslational control

Correct Answer
E. Posttranslational control

Explanation
Posttranslational control refers to the level of primary control in eukaryotic gene activity that involves modifications and changes to the polypeptide chain after it has been translated from mRNA. These modifications can include processes such as protein folding, addition of chemical groups, cleavage of certain segments, and protein degradation. These modifications are crucial for the protein to become functional and can regulate its activity, stability, and localization within the cell. Therefore, posttranslational control plays a significant role in determining the functionality and regulation of proteins in eukaryotic cells.

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6.

An enhancer site is

A.

Part of an operon.
B.

Found only in prokaryotes.
C.

Located at a distance from the gene it affects.
D.

An attachment site for RNA polymerase.

Correct Answer
C. Located at a distance from the gene it affects.

Explanation
An enhancer site is located at a distance from the gene it affects. Enhancer sites are regulatory DNA sequences that can increase the transcription of a gene. They can be located upstream, downstream, or even within an intron of the gene they affect. Enhancer sites are not limited to prokaryotes and can be found in both prokaryotes and eukaryotes. They function by binding to specific transcription factors, which then interact with the promoter region of the gene to enhance transcription.

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7.

"Jumping genes" that have the ability to move within and between chromosomes are called

A.

Introns.
B.

Oncogenes.
C.

Transposons.
D.

Retroviruses.
E.

Exons.

Correct Answer
C. Transposons.

Explanation
"Jumping genes" refers to transposons, which are DNA sequences that can move or "jump" within and between chromosomes. Introns are non-coding regions of DNA, oncogenes are genes that have the potential to cause cancer, retroviruses are a type of RNA virus, and exons are coding regions of DNA. Therefore, the correct answer is transposons.

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8.

An oncogene is

A.

A viral gene with no relation to the host cell's genes.
B.

A mutated form of a proto-oncogene.
C.

A bacterial gene that causes cancer in the host.
D.

Always seen in human cancer cells.
E.

A gene that turns off cellular reproduction.

Correct Answer
B. A mutated form of a proto-oncogene.

Explanation
An oncogene is a gene that has the potential to cause cancer. Proto-oncogenes are normal genes that regulate cell growth and division. When a proto-oncogene mutates, it becomes an oncogene, which can lead to uncontrolled cell growth and the development of cancer. Therefore, the correct answer is "a mutated form of a proto-oncogene."

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9.

The balance between stimulatory signals and inhibitory signals determines whether

A.

A cell is normal or malignant.
B.

A cell conducts normal metabolism or undergoes apoptosis.
C.

Proto-oncogenes are active.
D.

Tumor-suppressor genes are active.
E.

Both C and D.

Correct Answer
E. Both C and D.

Explanation
The balance between stimulatory signals and inhibitory signals is crucial in determining the activity of proto-oncogenes and tumor-suppressor genes. Proto-oncogenes can become active and promote cell division and growth when there is an imbalance towards stimulatory signals, leading to the development of cancer. On the other hand, tumor-suppressor genes are responsible for inhibiting cell division and promoting cell death (apoptosis) when there is an imbalance towards inhibitory signals. Therefore, both C and D are correct as an imbalance in stimulatory and inhibitory signals can affect the activity of both proto-oncogenes and tumor-suppressor genes.

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