Question 1

Genes whose expression is turned off in response to a substance in the environment are known as

Accepted Answer

A)  inducible genes. 
B)  repressible genes. 
C)  constitutive genes. 
D)  inducible genes and repressible genes. 
E)  All of these are correct. 
A)  inducible genes. 
B)  repressible genes. 
C)  constitutive genes. 
D)  inducible genes and repressible genes. 
E)  All of these are correct.

Question 2

When are the structural genes in the tryptophan operon transcribed?
1)Tryptophan is in abundance in the environment.
2)Tryptophan is absent from the environment.
3)Tryptophan is present in low amounts in the environment.

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  1 and 3 
E)  2 and 3 
A)  1 
B)  2 
C)  3 
D)  1 and 3 
E)  2 and 3

Question 3

UV light induces nondefective   prophages to enter the lytic pathway by which of the following mechanisms?

Accepted Answer

A)  SOS response 
B)  Conversion of RecA to a protease 
C)  Cleavage of the connector region of the  repressor 
D)  Prevention of dimerization of the DNA-binding domain of the repressor 
E)  All of these are correct. 
A)  SOS response 
B)  Conversion of RecA to a protease 
C)  Cleavage of the connector region of the  repressor 
D)  Prevention of dimerization of the DNA-binding domain of the repressor 
E)  All of these are correct.

Question 4

Which is true about an operator constitutive (Oc)mutation?

Accepted Answer

A)  An Oc mutation on the chromosome can affect the expression of structural genes on a plasmid. 
B)  The Oc mutation prevents the expression of a diffusible product that regulates the lac operon. 
C)  An F' I+P+ Oc Z-Y+A-/I+P+O+Z+Y+A+ merozygote expresses the enzymes of the lac operon constitutively. 
D)  The O? mutations act only in cis. 
E)  An F' I+P+ Oc Z+Y+A+/I+P+O+Z-Y-A- merozygote is inducible for the three enzymes of the lac operon. 
A)  An Oc mutation on the chromosome can affect the expression of structural genes on a plasmid. 
B)  The Oc mutation prevents the expression of a diffusible product that regulates the lac operon. 
C)  An F' I+P+ Oc Z-Y+A-/I+P+O+Z+Y+A+ merozygote expresses the enzymes of the lac operon constitutively. 
D)  The O? mutations act only in cis. 
E)  An F' I+P+ Oc Z+Y+A+/I+P+O+Z-Y-A- merozygote is inducible for the three enzymes of the lac operon.

Question 5

In the lac operon,what type of control is exhibited by the CAP/cAMP complex?

Accepted Answer

A)  Negative control 
B)  Positive control 
C)  Constitutive control 
D)  Negative control and positive control 
E)  All of these are correct. 
A)  Negative control 
B)  Positive control 
C)  Constitutive control 
D)  Negative control and positive control 
E)  All of these are correct.

Question 6

Which statement about catabolite repression is false?

Accepted Answer

A)  Glucose is the preferred energy source for E. coli and represses the utilization of other sugars. 
B)  The CAP protein is involved in catabolite repression of the lac operon. 
C)  RNA polymerase is the effector molecule that enables CAP to bind to the promoter. 
D)  The CAP protein and its effector molecule exert positive control over the transcription of the lac operon. 
E)  High glucose concentrations decrease the intracellular concentration of the effector molecule of the CAP protein. 
A)  Glucose is the preferred energy source for E. coli and represses the utilization of other sugars. 
B)  The CAP protein is involved in catabolite repression of the lac operon. 
C)  RNA polymerase is the effector molecule that enables CAP to bind to the promoter. 
D)  The CAP protein and its effector molecule exert positive control over the transcription of the lac operon. 
E)  High glucose concentrations decrease the intracellular concentration of the effector molecule of the CAP protein.

Question 7

What form of inhibition occurs when the product of a biosynthetic pathway inhibits the activity of the first enzyme in the pathway,rapidly arresting the biosynthesis of the product?

Accepted Answer

A)  Competitive inhibition 
B)  Feedback inhibition 
C)  Non-allosteric inhibition 
D)  Competitive inhibition and feedback inhibition 
E)  None of these are correct. 
A)  Competitive inhibition 
B)  Feedback inhibition 
C)  Non-allosteric inhibition 
D)  Competitive inhibition and feedback inhibition 
E)  None of these are correct.

Question 8

The process of turning on the expression of genes in response to a substance in the environment is called

Accepted Answer

A)  repression. 
B)  catabolite repression. 
C)  glucose effect. 
D)  induction. 
E)  positive feedback. 
A)  repression. 
B)  catabolite repression. 
C)  glucose effect. 
D)  induction. 
E)  positive feedback.

Question 9

Compare how a negative inducible control mechanism and a positive inducible control mechanism work in the presence and absence of an inducer.

Accepted Answer

In a negative,inducible control mechanis

Question 10

Which of the following substances is the inducer for the lac operon?

Accepted Answer

A)  Lactose 
B)  Tryptophan 
C)  cAMP 
D)  Glucose 
E)  CAP 
A)  Lactose 
B)  Tryptophan 
C)  cAMP 
D)  Glucose 
E)  CAP

Question 11

When temperate bacteriophages,such as phage l,enter the lysogenic pathway,covalently inserting their chromosome into the chromosome of the host,their lytic genes must be

Accepted Answer

A)  turned on. 
B)  turned off. 
C)  induced. 
D)  turned on and induced. 
E)  None of these are correct. 
A)  turned on. 
B)  turned off. 
C)  induced. 
D)  turned on and induced. 
E)  None of these are correct.

Question 12

Which of the following statements is true regarding the lac operon?

Accepted Answer

A)  The repressor binds to the promoter element. 
B)  Transcription is initiated by the binding of the inducer to the promoter. 
C)  The lac operon is unique because it is not subject to catabolite repression. 
D)  The promoter element is not essential for the transcription of the operon. 
E)  lacZ, lacY and lacA gene products are synthesized at low levels in the uninduced state. 
A)  The repressor binds to the promoter element. 
B)  Transcription is initiated by the binding of the inducer to the promoter. 
C)  The lac operon is unique because it is not subject to catabolite repression. 
D)  The promoter element is not essential for the transcription of the operon. 
E)  lacZ, lacY and lacA gene products are synthesized at low levels in the uninduced state.

Question 13

Genes whose expression is turned on in response to a substance in the environment are known as

Accepted Answer

A)  inducible genes. 
B)  repressible genes. 
C)  constitutive genes. 
D)  inducible genes and repressible genes. 
E)  All of these are correct. 
A)  inducible genes. 
B)  repressible genes. 
C)  constitutive genes. 
D)  inducible genes and repressible genes. 
E)  All of these are correct.

Question 14

Which characteristic is exhibited by transcription-termination signals found at the ends of most bacterial operons,such as the trp operon?

Accepted Answer

A)  They encode a nascent RNA with the potential to form hydrogen-bonded hairpin structures. 
B)  They contain the operator region to which the repressor binds to shut off transcription. 
C)  They contain the site for the binding of the CAP-cAMP complex to affect catabolite repression. 
D)  They contain the binding site for the repressor-corepressor complex. 
E)  They begin with the sequence ATG. 
A)  They encode a nascent RNA with the potential to form hydrogen-bonded hairpin structures. 
B)  They contain the operator region to which the repressor binds to shut off transcription. 
C)  They contain the site for the binding of the CAP-cAMP complex to affect catabolite repression. 
D)  They contain the binding site for the repressor-corepressor complex. 
E)  They begin with the sequence ATG.

Question 15

How do promoter mutations change the expression of the lac operon genes?
1)They change the inducibility of the lac operon.
2)They modify the levels of gene expression in the induced and uninduced state.
3)They change the frequency of initiation of lac operon transcription.

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  1 and 2 
E)  2 and 3 
A)  1 
B)  2 
C)  3 
D)  1 and 2 
E)  2 and 3

Question 16

Which of the following is a constituent of the lac operon promoter?
1)RNA polymerase binding site
2)CAP binding site
3)lac I gene

Accepted Answer

A)  1 
B)  2 
C)  3 
D)  1 and 2 
E)  2 and 3 
A)  1 
B)  2 
C)  3 
D)  1 and 2 
E)  2 and 3

Question 17

The enzyme b-galactosidase is encoded by

Accepted Answer

A)  lacA. 
B)  lacy. 
C)  lacZ. 
D)  lacI. 
E)  both lacA and lacY. 
A)  lacA. 
B)  lacy. 
C)  lacZ. 
D)  lacI. 
E)  both lacA and lacY.

Question 18

Genes encoding products that regulate the expression of other genes are known as

Accepted Answer

A)  positive control genes. 
B)  negative control genes. 
C)  regulator genes. 
D)  transcriptional genes. 
E)  translatable genes. 
A)  positive control genes. 
B)  negative control genes. 
C)  regulator genes. 
D)  transcriptional genes. 
E)  translatable genes.

Question 19

Draw a sketch of a simplistic operon with 4 structural genes.

Accepted Answer

--Promoter--Operator

Question 20

Which level of gene regulation occurs via the action of inducible and repressible genes?

Accepted Answer

A)  Replication 
B)  Transcription 
C)  Translation 
D)  Replication and transcription 
E)  Replication and translation 
A)  Replication 
B)  Transcription 
C)  Translation 
D)  Replication and transcription 
E)  Replication and translation

Exam 18: Regulation Of Gene Expression In Prokaryotes

Genes whose expression is turned off in response to a substance in the environment are known as

When are the structural genes in the tryptophan operon transcribed? 1)Tryptophan is in abundance in the environment. 2)Tryptophan is absent from the environment. 3)Tryptophan is present in low amounts in the environment.

UV light induces nondefective prophages to enter the lytic pathway by which of the following mechanisms?

Which is true about an operator constitutive (Oc)mutation?

In the lac operon,what type of control is exhibited by the CAP/cAMP complex?

Which statement about catabolite repression is false?

What form of inhibition occurs when the product of a biosynthetic pathway inhibits the activity of the first enzyme in the pathway,rapidly arresting the biosynthesis of the product?

The process of turning on the expression of genes in response to a substance in the environment is called

Compare how a negative inducible control mechanism and a positive inducible control mechanism work in the presence and absence of an inducer.

Which of the following substances is the inducer for the lac operon?

When temperate bacteriophages,such as phage l,enter the lysogenic pathway,covalently inserting their chromosome into the chromosome of the host,their lytic genes must be

Which of the following statements is true regarding the lac operon?

Genes whose expression is turned on in response to a substance in the environment are known as

Which characteristic is exhibited by transcription-termination signals found at the ends of most bacterial operons,such as the trp operon?

How do promoter mutations change the expression of the lac operon genes? 1)They change the inducibility of the lac operon. 2)They modify the levels of gene expression in the induced and uninduced state. 3)They change the frequency of initiation of lac operon transcription.

Which of the following is a constituent of the lac operon promoter? 1)RNA polymerase binding site 2)CAP binding site 3)lac I gene

The enzyme b-galactosidase is encoded by

Genes encoding products that regulate the expression of other genes are known as

Draw a sketch of a simplistic operon with 4 structural genes.

Which level of gene regulation occurs via the action of inducible and repressible genes?

The Science Of Genetics

Cellular Reproduction

Mendelism The Basic Principles Of Inheritance

Extensions Of Mendelism

The Chromosomal Basis Of Mendelism

Variation In Chromosome Number And Structure

Linkage,Crossing Over,And Chromosome Mapping In …

The Genetics Of Bacteria And Their Viruses

DNA And The Molecular Structure Of Chromosomes

Replication Of DNA And Chromosomes

Transcription And RNA Processing

Translation And The Genetic Code

Mutation,DNA Repair,And Recombination

The Techniques Of Molecular Genetics

Genomics

Applications Of Molecular Genetics

Transposable Genetics Elements

Regulation Of Gene Expression In Eukaryotes

The Genetic Control Of Animal Development

The Genetic Basis Of Cancer

Inheritance Of Complex Traits

Population Genetics

Evolutionary Genetics

Filters

Which is true about an operator constitutive (O^c)mutation?