Genetics And Gene Mutation Trivia Quiz

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  • 1/29 Questions

    The repressor is a type of regulator protein that binds to a region of DNA in the promoter of a gene called the ________ and prevents transcription from taking place. 

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About This Quiz

A lot of genetic disorders can be labeled as being caused by gene mutation, where a person’s DNA undergoes different changes. The mutations can either be deletions, insertions, or base substitutions. The quiz below is designed to test your understanding of gene and gene mutations, think that you are well informed to tackle it? Why don’t you give it a shot and get to find out!

Genetics And Gene Mutation Trivia Quiz - Quiz

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  • 2. 

    A promoter that affects only genes that are on the same piece of DNA is  ____ -acting. 

    Explanation
    A promoter that affects only genes that are on the same piece of DNA is referred to as "cis-acting." The term "cis" in this context indicates that the regulatory element is located on the same DNA molecule as the genes it influences. This is in contrast to "trans-acting" elements, which can regulate genes located on different DNA molecules. The concept of cis-acting elements is important in understanding gene regulation and the coordination of gene expression within a specific genomic region.

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  • 3. 

    An inducible gene is transcribed when a specific substance is present.  

    • True

    • False

    Correct Answer
    A. True
    Explanation
    An inducible gene is a gene that is transcribed, or activated, when a specific substance is present. This means that the presence of this substance triggers the transcription of the gene, leading to the production of the corresponding protein. Therefore, the statement "An inducible gene is transcribed when a specific substance is present" is true.

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  • 4. 

    When a structural gene is under negative inducible control, a mutation that eliminates the repressor protein will cause the structural gene to be constitutively expressed.  

    • True

    • False

    Correct Answer
    A. True
    Explanation
    When a structural gene is under negative inducible control, it means that the gene is normally repressed by a repressor protein. In this case, if a mutation occurs that eliminates the repressor protein, there will be no inhibition of the gene expression. As a result, the structural gene will be expressed continuously or constitutively, regardless of the presence or absence of an inducer. Therefore, the statement "a mutation that eliminates the repressor protein will cause the structural gene to be constitutively expressed" is true.

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  • 5. 

    A repressible gene is controlled by a regulatory protein that inhibits transcription. 

    • True

    • False

    Correct Answer
    A. True
    Explanation
    A repressible gene is controlled by a regulatory protein that inhibits transcription. This means that the gene is normally active and producing its corresponding protein, but can be turned off or repressed by the presence of a regulatory protein. This regulatory protein binds to the gene's promoter region and prevents the RNA polymerase enzyme from binding and initiating transcription. Therefore, the statement "A repressible gene is controlled by a regulatory protein that inhibits transcription" is true.

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  • 6. 

    For a gene under positive repressible control, the normal state is transcription of a gene, stimulated by a transcriptional activator.  

    • True

    • False

    Correct Answer
    A. True
    Explanation
    In positive repressible control, the normal state is indeed transcription of a gene, which is stimulated by a transcriptional activator. This means that the gene is normally being transcribed unless it is repressed by a specific factor. Therefore, the statement "the normal state is transcription of a gene, stimulated by a transcriptional activator" is true.

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  • 7. 

    Regulatory genes are genes whose products are either RNA or proteins. 

    • True

    • False

    Correct Answer
    A. True
    Explanation
    Regulatory genes are responsible for controlling the expression of other genes. They produce products that can be either RNA or proteins. This means that the statement "Regulatory genes are genes whose products are either RNA or proteins" is true.

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  • 8. 

    Transcriptional control that acts by regulating the continuation of transcription is called

    Correct Answer
    attenuation
    Explanation
    Attenuation is a type of transcriptional control that regulates the continuation of transcription. It occurs in certain bacterial operons where the rate of transcription can be affected by the presence or absence of specific molecules. Attenuation involves the formation of alternative RNA secondary structures during transcription, which can either allow or prevent the continuation of transcription. This mechanism allows the cell to quickly respond to changes in the availability of certain molecules and adjust gene expression accordingly.

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  • 9. 

    Since the binding of the inducer to the repressor prevents it from binding to DNA by causing a conformational change in its structure, it is called an __________ protein.

    Correct Answer
    allosteric
    Explanation
    The inducer molecule binds to the repressor protein and causes a change in its structure, which prevents the repressor from binding to DNA. This type of regulation, where the binding of a molecule at one site affects the activity at another site, is known as allosteric regulation. Therefore, the correct answer is allosteric.

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  • 10. 

    In the absence of allolactose, the lac operon is constitutively transcribed.

    • True

    • False

    Correct Answer
    A. False
    Explanation
    In the absence of allolactose, the lac operon is not constitutively transcribed. The lac operon is a group of genes involved in the metabolism of lactose in bacteria. It is regulated by a repressor protein that binds to the operator region and prevents transcription of the genes. In the absence of allolactose, the repressor protein remains bound to the operator, blocking transcription. When allolactose is present, it binds to the repressor, causing a conformational change that releases the repressor from the operator, allowing transcription to occur. Therefore, the absence of allolactose does not lead to constitutive transcription of the lac operon.

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  • 11. 

    It is possible for a repressor to negatively regulate the expression of an operon because

    • the repressor induces the expression of inducer.

    • One of the genes expressed in the operon negatively regulates the repressor.

    • The repressor binding site overlaps the promoter site of the operon allowing it to physically block the binding of RNA polymerase.

    • The repressor binding site on the DNA overlaps with the translation start site.

    Correct Answer
    A. The repressor binding site overlaps the promoter site of the operon allowing it to physically block the binding of RNA polymerase.
    Explanation
    The correct answer is that the repressor binding site overlaps the promoter site of the operon, allowing it to physically block the binding of RNA polymerase. This means that when the repressor binds to the DNA, it prevents RNA polymerase from binding to the promoter region and initiating transcription. As a result, the expression of the operon is negatively regulated, as transcription cannot occur.

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  • 12. 

    What is the function of cAMP in regulation of the lac operon?

    • It activates a repressor protein.

    • It activates a activator protein.

    • It inactivates a repressor protein.

    • It inactivates a activator protein.

    Correct Answer
    A. It activates a activator protein.
    Explanation
    cAMP, or cyclic adenosine monophosphate, plays a crucial role in the regulation of the lac operon. In the presence of glucose, cAMP levels are low, and the lac operon remains inactive. However, when glucose levels are low, cAMP levels increase, and cAMP binds to the activator protein called CAP (catabolite activator protein). The cAMP-CAP complex then binds to the promoter region of the lac operon, enhancing the binding of RNA polymerase and promoting transcription of the lac genes. Therefore, cAMP activates the activator protein CAP, which is required for the expression of the lac operon.

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  • 13. 
    Which parts of the DNA region shown in the diagram encode proteins?  Use the following diagram of the lac I gene and lac operon for questions 24-25.  (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator - ProProfs

    Which parts of the DNA region shown in the diagram encode proteins?  Use the following diagram of the lac I gene and lac operon for questions 24-25.  (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator

    • P

    • P, O, Z, Y, A

    • I, Z, Y, A

    • I, P, O, Z, Y, A

    Correct Answer
    A. I, Z, Y, A
    Explanation
    The correct answer is I, Z, Y, A. This is because the lac I gene and lac operon structural genes Z, Y, and A are responsible for encoding proteins. The lac I gene encodes the lac repressor protein, which regulates the expression of the lac operon. The lac operon structural genes Z, Y, and A encode the proteins necessary for the metabolism of lactose. The lac promoter (P) and operator (O) are regulatory regions of the DNA and do not directly encode proteins.

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  • 14. 

    What is the function of allolactose in regulation of the lac operon?

    • Inducer

    • Repressor

    • Activator

    • Promoter

    • Regulatory protein

    Correct Answer
    A. Inducer
    Explanation
    Allolactose acts as an inducer in the regulation of the lac operon. It binds to the repressor protein, causing a conformational change that prevents it from binding to the operator region of the operon. This allows RNA polymerase to bind to the promoter region and transcribe the genes involved in lactose metabolism. Therefore, allolactose helps to activate the lac operon by relieving the repression imposed by the repressor protein.

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  • 15. 

    When a structural gene is under positive inducible control, a mutation that eliminates the activator protein will cause the structural gene to be constitutively expressed.  

    • True

    • False

    Correct Answer
    A. False
    Explanation
    When a structural gene is under positive inducible control, it means that the expression of the gene is normally turned off and requires the presence of an activator protein to be turned on. If a mutation occurs that eliminates the activator protein, the gene will not be able to be turned on and therefore will not be constitutively expressed. Therefore, the correct answer is false.

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  • 16. 

    In the absence of tryptophan, the genes of the trp operon are not expressed.  

    • True

    • False

    Correct Answer
    A. False
    Explanation
    In the absence of tryptophan, the genes of the trp operon are actually expressed. The trp operon is a set of genes responsible for the synthesis of tryptophan in bacteria. When tryptophan is present in the environment, it binds to a repressor protein, which then binds to the operator region of the operon, preventing the expression of the genes. However, in the absence of tryptophan, the repressor protein is unable to bind to the operator region, allowing the genes to be expressed and leading to the synthesis of tryptophan. Therefore, the statement that the genes of the trp operon are not expressed in the absence of tryptophan is false.

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  • 17. 

    What modification neutralizes the charges on histones that promote ionic interaction with DNA?

    • Phosphorylation

    • Demethylation

    • Acetylation

    • Polyadenylation

    Correct Answer
    A. Acetylation
    Explanation
    Acetylation is the modification that neutralizes the charges on histones that promote ionic interaction with DNA. Acetylation involves the addition of an acetyl group to the histone proteins, which reduces the positive charge on the histones. This reduction in positive charge weakens the interaction between histones and DNA, allowing for a more relaxed and open chromatin structure. This modification is important for gene expression regulation, as it allows for easier access of transcription factors and other proteins to the DNA.

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  • 18. 

    E. coli lac operon control by CAP

    • Negative inducible

    • Negative repressible

    • Positive inducible

    • Positive repressible

    Correct Answer
    A. Positive inducible
    Explanation
    The lac operon in E. coli is controlled by CAP (catabolite activator protein). CAP acts as a positive regulator, meaning it enhances the transcription of the lac operon genes in the presence of an inducer molecule, such as lactose. This is known as positive inducible control because the presence of the inducer molecule induces the expression of the lac operon genes. Therefore, the correct answer is positive inducible.

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  • 19. 

    A gene is any DNA sequence that is transcribed into a mRNA molecule.

    • True

    • False

    Correct Answer
    A. False
    Explanation
    This statement is false because not all DNA sequences are transcribed into mRNA molecules. Only certain sections of DNA, known as genes, are transcribed into mRNA. Genes contain the instructions for building proteins, and these instructions are transcribed into mRNA through a process called transcription. So, while genes are DNA sequences that are transcribed into mRNA, not all DNA sequences are genes.

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  • 20. 

    An operon is controlled by a repressor.  When the repressor binds to a small molecule, it binds to DNA near the operon.  The operon is constitutively expressed if a mutation prevents the repressor from binding to the small molecule.

    • Negative inducible

    • Negative repressible

    • Positive inducible

    • Positive repressible

    Correct Answer
    A. Negative repressible
    Explanation
    An operon is controlled by a repressor that binds to DNA near the operon. In the case of negative repressible operons, the repressor is normally bound to the operator region, preventing transcription of the operon. However, when a small molecule binds to the repressor, it undergoes a conformational change and is released from the operator, allowing transcription to occur. Therefore, the operon is repressed in the absence of the small molecule, and its expression is negatively regulated.

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  • 21. 

    A mutant E. coli strain, grown under conditions that normally induce the lac operon, produces high amounts of ß-galactosidase.  What is a possible genotype of the cells?

    • lacI+ lacP+ lacO+ lacZ– lacY+ lacA+

    • . lacI+ lacP+ lacOc lacZ+ lacY+ lacA+

    • LacI– lacP+ lacO+ lacZ– lacY+ lacA+

    • LacI+ lacP– lacO+ lacZ+ lacY+ lacA+

    Correct Answer
    A. . lacI+ lacP+ lacOc lacZ+ lacY+ lacA+
    Explanation
    The lac operon is a group of genes involved in the metabolism of lactose in E. coli. The lacI gene encodes the lac repressor protein, which binds to the operator region (lacO) and prevents the expression of the lac genes. In the given genotype, lacI+ indicates that the lac repressor is functional, lacP+ indicates that the promoter region is intact, lacOc indicates a constitutive mutation in the operator region, lacZ+ indicates the presence of the β-galactosidase gene, lacY+ indicates the presence of the lactose permease gene, and lacA+ indicates the presence of the transacetylase gene. Since lacOc is a constitutive mutation, it causes the lac operon to be expressed all the time, leading to the high production of β-galactosidase.

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  • 22. 

    E. coli lac operon control by lac I

    • Negative inducible

    • Negative repressible

    • Positive inducible

    • Positive repressible

    Correct Answer
    A. Negative inducible
    Explanation
    The lac operon in E. coli is controlled by the lac I gene, which produces a repressor protein. This repressor protein binds to the operator region of the operon, preventing the transcription of the lac genes. However, in the presence of lactose, the lactose molecules bind 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 genes. Therefore, the lac operon control by lac I is an example of negative inducible regulation, as the presence of an inducer (lactose) relieves the repression of the operon.

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  • 23. 

    For a gene under negative repressible control, a small molecule is required to prevent the gene's repressor from binding to DNA.

    • True

    • False

    Correct Answer
    A. False
    Explanation
    In negative repressible control, a small molecule is required to bind to the gene's repressor and enable it to bind to DNA, thereby preventing gene expression. This is the opposite of the statement given in the question, which states that the small molecule prevents the gene's repressor from binding to DNA. Therefore, the correct answer is False.

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  • 24. 

    An example of a gene product encoded by a regulatory gene is

    • Beta-galactosidase enzyme.

    • Allolactose

    • Repressor protein.

    • Operator

    Correct Answer
    A. Repressor protein.
    Explanation
    A regulatory gene encodes for a repressor protein, which is a molecule that binds to the operator region of DNA and prevents the transcription of certain genes. This repressor protein helps regulate gene expression by blocking the binding of RNA polymerase to the promoter region, thus inhibiting the initiation of transcription. In this case, the repressor protein is an example of a gene product encoded by a regulatory gene.

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  • 25. 

    If a mutation prevents the formation of the antiterminator 2 + 3 loop in the trp operon, what would be the effect?

    • Transcription only when tryptophan is absent

    • Transcription only when tryptophan is present

    • Constitutive attenuation of transcription

    • Constitutive transcription

    Correct Answer
    A. Constitutive attenuation of transcription
    Explanation
    If a mutation prevents the formation of the antiterminator 2 + 3 loop in the trp operon, it would result in constitutive attenuation of transcription. The antiterminator 2 + 3 loop is responsible for preventing the termination of transcription in the presence of tryptophan. Without this loop, transcription would be attenuated, meaning it would be prematurely terminated regardless of the presence or absence of tryptophan. This would lead to a constant level of transcription, resulting in constitutive attenuation of transcription.

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  • 26. 

    A mutant E. coli strain, grown under conditions that normally induce the lac operon, does not produce ß-galactosidase.  What is a possible genotype of the cells?

    • LacI+ lacP+ lacO+ lacZ+ lacY– lacA+

    • LacI+ lacP+ lacOc lacZ+ lacY+ lacA+

    • Lacl+ lacP+ lacO+ lacZ+ lacY+ lacA+

    • LacI+ lacP– lacO+ lacZ+ lacY+ lacA+

    Correct Answer
    A. LacI+ lacP– lacO+ lacZ+ lacY+ lacA+
    Explanation
    A possible genotype of the cells could be lacI+ lacP– lacO+ lacZ+ lacY+ lacA+. This genotype suggests that the mutant E. coli strain has a mutation in the lacP gene, which is responsible for the production of the lac repressor protein. Without the lac repressor protein, the lac operon is not properly regulated, leading to the absence of ß-galactosidase production. The other genes (lacI, lacO, lacZ, lacY, lacA) are still functional, allowing for the production of other proteins and enzymes in the lac operon.

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  • 27. 

    An operon is controlled by a repressor.  When the repressor binds to a small molecule, it is released from binding to DNA near the operon.  The operon is never expressed if a mutation prevents the repressor from binding to the small molecule.

    • Negative inducible

    • Negative repressible

    • Positive inducible

    • Positive repressible

    Correct Answer
    A. Negative inducible
    Explanation
    An operon is controlled by a repressor, which means that the repressor protein binds to the DNA near the operon and prevents its expression. However, in the case of a negative inducible operon, the repressor is released from binding to the DNA when it binds to a small molecule, such as an inducer. This allows the operon to be expressed and the genes within it to be transcribed. Therefore, if a mutation prevents the repressor from binding to the small molecule, the operon will never be expressed, indicating that it is a negative inducible operon.

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  • 28. 

    In the previous diagram, if there is a mutation in P and I, which of the following is true?

    • These are mutations that are, respectively, cis and trans acting on lac operon expression.

    • These are mutations that are, respectively, trans and cis acting on lac operon expression.

    • These will affect the expression of I only.

    • These will affect the expression of only Z, Y, and A.

    Correct Answer
    A. These are mutations that are, respectively, cis and trans acting on lac operon expression.
    Explanation
    The correct answer is that the mutations in P and I are respectively cis and trans acting on lac operon expression. This means that the mutation in P affects the expression of genes on the same DNA molecule, while the mutation in I affects the expression of genes on a different DNA molecule. This suggests that the mutations have different effects on lac operon expression, with the cis mutation likely having a more direct and localized effect, while the trans mutation may have a more indirect and widespread effect.

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  • 29. 
    Where would the lac repressor be bound in a (nonmutant) E. coli cell that is growing in low glucose and high lactose? Use the following diagram of the lac I gene and lac operon for questions 24-25.  (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator - ProProfs

    Where would the lac repressor be bound in a (nonmutant) E. coli cell that is growing in low glucose and high lactose? Use the following diagram of the lac I gene and lac operon for questions 24-25.  (I = lac repressor gene; Z, Y, A = lac operon structural genes; P = lac promoter; O = lac operator

    • P

    • O

    • P and O

    • I, P, O

    • The repressor would not be bound.

    Correct Answer
    A. The repressor would not be bound.
    Explanation
    In a nonmutant E. coli cell that is growing in low glucose and high lactose, the lac repressor would not be bound. The lac repressor is a protein that binds to the lac operator, which is a DNA sequence located upstream of the lac operon. In the presence of lactose, the lac repressor undergoes a conformational change and is unable to bind to the lac operator. This allows for the expression of the lac operon, which includes genes involved in lactose metabolism. In low glucose conditions, the cAMP-CAP complex is formed, which further enhances the expression of the lac operon. Therefore, in the given conditions, the lac repressor would not be bound to the lac operator.

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  • Sep 04, 2024
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