Question 1

Which of the following is true of transcriptional activator proteins?
a.They destabilize the basal transcription apparatus.
b.Some have acetyltransferase activity.
c.They do not bind promoter sequences.
d.All of the above are true.

Accepted Answer

Transcriptional activator proteins may have acetyltransferase activity which can modify histones and promote transcription. They do not destabilize the basal transcription apparatus and they usually bind to specific promoter sequences to increase transcription. Therefore, only choice B is true.

Question 2

The trp operon repressor has two binding sites.In sequential order,what two things bind the repressor?
a.DNA,tryptophan
b.first DNA site,second DNA site
c.first trptophan molecule,second tryptophan molecule
d.tryptophan,DNA

tryptophan , DNA

Accepted Answer

The trp operon repressor first binds to tryptophan, which activates it to then bind to the DNA at the operator site, inhibiting transcription.

Question 3

Regulation of gene activity can occur at several stages,such as _________.
a.transcription
b.translation
c.posttranslational modification
d.mRNA processing and stability
e.all of the above

all of the above

Accepted Answer

Regulation of gene activity can occur at several stages,such as _________.
a.transcription
b.translation
c.posttranslational modification
d.mRNA processing and stability
e.all of the above

all of the above

Question 4

To activate the transcription of permease and the whole lac operonlactose needs to be present in the cell.How can lactose get in the cell when the permease gene is not activated?
a.The repressed lac operon is never completely repressed.
b.There is a second permease in the genome that initially transports lactose.
c.Lactose freely moves across the plasma membrane.
d.Though the lac operon has been studied for many years,this mystery is unsolved.

Accepted Answer

The repressed lac operon is never completely repressed, allowing a small amount of permease to be produced, which can transport lactose into the cell.

Question 5

What is the role of insulators?&#10;a.They maintain nucleosome structures.&#10;b.They recruit transcriptional activator proteins.&#10;c.They recruit the basal transcription apparatus.&#10;d.They block the role of enhancers.&#10;e.All of the above are true.

Accepted Answer

Insulators block the role of enhancers by preventing their interaction with promoters and thus, maintain the correct regulation of gene expression.

Question 6

siRNA and miRNA inhibit gene expression by all of the following EXCEPT
a.cleaving mRNA
b.altering chromatin structure
c.stimulating RNA degradation
d.stabilizing translation machinery
e.all of the above

Accepted Answer

siRNA and miRNA function by targeting mRNA for degradation or inhibiting its translation. They do not directly alter chromatin structure or stimulate RNA degradation by themselves. Cleaving mRNA is a mechanism used by siRNA, but not miRNA. Therefore, choice D is the correct answer as it is the only one that is not affected by siRNA or miRNA.

Question 7

An__________ operon is normally turned on,and it is turned off by an_________.&#10;a.inducible; activator&#10;b.inducible; repressor&#10;c.repressible; activator&#10;d.repressible; repressor

Accepted Answer

A repressible operon is typically active and is turned off by a repressor when a specific molecule is present.

Question 8

Which of the following chromatin changes will repress gene transcription?
a.histone acetylation
b.chromatin-remodeling complexes that reposition nucleosomes
c.DNA not methylated
d.all of the above

Accepted Answer

DNA methylation is a known mechanism for gene repression. Histone acetylation and chromatin-remodeling complexes that reposition nucleosomes usually lead to transcriptional activation. Therefore, the correct choice is C.

Question 9

What kind of gene has a product that interacts with other nucleotide sequences,affecting their transcription or translation?
a.constitutive gene
b.regulatory gene
c.structural gene
d.none of the above

Accepted Answer

Regulatory genes produce products such as transcription factors or repressors, which bind to specific nucleotide sequences and either enhance or inhibit transcription of nearby genes. This interaction can also affect translation by either promoting or impeding the binding of ribosomes to mRNA. Constitutive genes and structural genes do not have a direct role in regulating gene expression.

Question 10

A typical operon contains several regions.Which region is where a regulator protein binds?&#10;a.structural genes&#10;b.promoter&#10;c.operator&#10;d.none of the above

Accepted Answer

The operator region is where a regulator protein binds to control the transcription of the structural genes. The promoter region is where RNA polymerase binds to initiate transcription, and the structural genes are the genes that are transcribed into mRNA and then translated into proteins.

Deck 12: Control of Gene Expression