The Regulation Of Gene Expression! Trivia Quiz

1.

The cluster of genes important in lactose metabolism in E. coli, along with the controlling DNA elements for these genes are known by the very brief acronym:

A.

Lac operon
B.

Lactose regulating gene and their control elements
C.

Genes that regulate the breakdown of the disaccharide lactose plus the regulatory sequences near them
D.

The regulator gene, CAP-binding site, promoter, operator, 5' UTR coding region, ß-galactosidase gene, galactoside permease gene, and transacetylase gene

Correct Answer
A. Lac operon

Explanation
The correct answer is "lac operon" because it refers to the cluster of genes important in lactose metabolism in E. coli, along with the controlling DNA elements for these genes. The other options provided in the question describe various components or aspects of the lac operon, but only "lac operon" encompasses the entire cluster of genes and their controlling elements.

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2.

In an E. coli culture growing in medium with lactose, the lac operon is on because ______ cannot bind to a DNA site adjacent to the promoter.

Correct Answer
repressor protein
the repressor protein
RP
the RP
a repressor protein

Explanation
The lac operon in E. coli is turned on when the repressor protein cannot bind to a DNA site adjacent to the promoter. The repressor protein normally binds to the operator region of the lac operon, preventing the transcription of genes involved in lactose metabolism. However, in the presence of lactose, it binds to the lactose molecule instead, causing a conformational change that prevents it from binding to the operator. This allows RNA polymerase to bind to the promoter and initiate transcription of the lac operon genes, enabling the metabolism of lactose. The terms "repressor protein," "the repressor protein," "RP," "the RP," and "a repressor protein" all refer to the same concept in this context.

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3.

In the lac operon of E. coli, repressor protein binds to the ________.

Correct Answer
operator

Explanation
In the lac operon of E. coli, the repressor protein binds to the operator. The operator is a specific DNA sequence located near the promoter region of the lac operon. When the repressor protein binds to the operator, it prevents RNA polymerase from binding to the promoter and transcribing the genes involved in lactose metabolism. This binding occurs in the absence of lactose or when glucose is present, signaling that lactose is not needed for energy production. When lactose is present, it binds to the repressor protein, causing a conformational change that prevents it from binding to the operator, allowing RNA polymerase to transcribe the genes and produce the necessary enzymes for lactose metabolism.

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4.

When lactose in an E. coli culture, allolactose binds to the _______ .

Correct Answer
repressor protein

Explanation
Allolactose is an inducer molecule that binds to the repressor protein in E. coli. The repressor protein normally binds to the operator region of the lactose operon, preventing the transcription of genes involved in lactose metabolism. However, when allolactose binds to the repressor protein, it causes a conformational change that prevents the repressor from binding to the operator. This allows RNA polymerase to bind to the promoter region and initiate transcription of the lactose genes, enabling E. coli to metabolize lactose.

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5.

When _________ is bound to repressor protein, repressor protein cannot bind to the operator.

Correct Answer
allolactose

Explanation
When allolactose is bound to the repressor protein, it causes a conformational change in the protein's structure. This change prevents the repressor protein from binding to the operator region of the DNA. As a result, the binding site for the repressor protein is blocked, allowing RNA polymerase to bind to the promoter region and initiate transcription of the genes downstream. Therefore, the presence of allolactose prevents the repressor protein from inhibiting gene expression.

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6.

The lac operon of E. coli is transcribed when:

A.

Lactose is present.
B.

Repressor protein is bound to the operator.
C.

Allolactose binds to the promoter.
D.

All of the above.

Correct Answer
A. Lactose is present.

Explanation
The lac operon of E. coli is a group of genes involved in the metabolism of lactose. It is transcribed when lactose is present in the environment. Lactose acts as an inducer and binds to the repressor protein, causing a conformational change that prevents it from binding to the operator. This allows RNA polymerase to bind to the promoter and initiate transcription of the lac operon genes. The presence of allolactose, a derivative of lactose, also contributes to the activation of the operon by binding to the promoter. Therefore, the correct answer is lactose is present.

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7.

The site on the DNA where a specific protein binds that results in RNA polymerase binding to the promoter are called the _________.

Correct Answer
enhancer

Explanation
The correct answer is enhancer. Enhancers are specific sites on DNA where proteins bind, and this binding helps RNA polymerase to bind to the promoter. Enhancers play a crucial role in regulating gene expression by increasing the transcription of specific genes. They can be located far away from the genes they regulate and can act over long distances through DNA looping and other mechanisms.

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8.

A (an) ________ is a small RNA molecule that is part of a RISC and binds precisely to an mRNA and results in its cleavage.

Correct Answer
siRNA
small interfering RNA

Explanation
An siRNA, or small interfering RNA, is a small RNA molecule that is part of a RISC (RNA-induced silencing complex) and binds specifically to a messenger RNA (mRNA) molecule, causing it to be cleaved or degraded. This process is a key mechanism in RNA interference (RNAi), which regulates gene expression by preventing the translation of specific mRNA molecules. Therefore, siRNA is the correct answer as it accurately describes the small RNA molecule that binds to mRNA and leads to its cleavage.

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9.

A (an) ________ is a small RNA molecule that is part of a RISC and binds imprecisely to an mRNA and turns off its translation.

Correct Answer
miRNA
microRNA
micro RNA

Explanation
miRNA, microRNA, or micro RNA are all correct answers for this question. These terms refer to small RNA molecules that are part of a RISC (RNA-induced silencing complex) and have the ability to bind imprecisely to an mRNA molecule, thereby inhibiting or turning off its translation. These molecules play a crucial role in gene regulation and have been extensively studied in various biological processes.

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10.

When __________ occurs, a gene's pre-mRNA can result in the synthesis of two different polypeptides.

Correct Answer
alternate splicing

Explanation
Alternate splicing is a process in which different combinations of exons are included or excluded from the final mRNA molecule during gene expression. This can result in the synthesis of multiple isoforms or variants of a protein from a single gene. By selectively including or excluding certain exons, the mRNA can be processed in different ways, leading to the production of different polypeptides with distinct functions or properties. Therefore, when alternate splicing occurs, a gene's pre-mRNA can result in the synthesis of two different polypeptides.

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