Question 1

DNA controls

Accepted Answer

A)   in which tissues genes are expressed.
B)   when genes are expressed.
C)   for how long genes are expressed.
D)   gene expression in response to the environment.
E)   All of the answers are correct. E

Question 2

An activator-binding site that is located on the same chromosome as the gene it affects is called

Accepted Answer

A)   a monosome.
B)   an enhancer.
C)   an adaptor molecule.
D)   a promoter.
E)   an operator. B

Question 3

Which of the following statements about protein synthesis and regulation of genes is CORRECT?

Accepted Answer

A)   Transcription and translation require an energy input.
B)   Protein modification is the most common means for the control of gene expression.
C)   All cells can induce or repress genes in response to environmental cues.
D)   Bacteria continuously manufacture a set of enzymes such that they can utilise most commonly found substrates.
E)   mRNA is produced at a constant rate. A

Question 4

In the regulation of the lac operon in Escherichia coli, cyclic AMP

Accepted Answer

A)   is a small metabolite that binds with lactose to increase transcription of the lac operon.
B)   increases in concentration when glucose is present in the cell.
C)   is produced from glucose to inhibit the binding of RNA polymerase to the lac operon.
D)   is involved in the positive regulation of the lac operon via its allosteric interaction with the catabolite activator protein.
E)   prevents the RNA polymerase from binding to the promoter region via its allosteric interaction with the catabolite activator protein.

Question 5

The addition of acetyl groups to histones

Accepted Answer

A)   makes the histones less positively charged.
B)   reduces the strength of the ionic bond between histones and DNA.
C)   can be a way for enhancer-binding complexes that activate transcription to exert their regulatory effect.
D)   plays a critical role in eukaryote gene expression.
E)   All of the answers are correct.

Question 6

Which of the following statements about promoters in prokaryotic genes is CORRECT?

Accepted Answer

A)   Promoters are adjacent to the 3' end of the transcription unit.
B)   A promoter is the site of binding DNA polymerase prior to the initiation of transcription.
C)   Promoters are adjacent to the operon, the site of binding of specific regulatory proteins.
D)   Promoters are not involved in the regulation of gene expression.
E)   None of the answers are correct.

Question 7

Genes involved in the synthesis of amino acids are usually only expressed when the amino acids are running out. This is an example of

Accepted Answer

A)   positive regulation.
B)   negative regulation.
C)   no regulation.
D)   direct inhibition of transcription by specific amino acids.
E)   constitutive expression.

Question 8

In the regulation of the lac operon in Escherichia coli, allolactose

Accepted Answer

A)   is one of the products of lactose metabolism by the cell.
B)   has an allosteric interaction with the repressor protein, which makes the repressor protein unable to bind to the operator region.
C)   results in an increased rate of transcription of the lacZ, lacY and lacA genes.
D)   All of the answers are correct.
E)   None of the answers are correct.

Question 9

If a regulatory gene that produced microRNAs had a mutation, the resulting microRNA would

Accepted Answer

A)   remain the same if the mutation was a nonsense mutation.
B)   show lower efficacy if the mutation was a missense mutation that was not removed during post-translational processing.
C)   show the same efficacy if the mutation was a missense mutation, but was removed during post-transcriptional processing.
D)   remain the same if the mutation was a nonsense mutation and show the same efficacy if the mutation was a missense mutation, but was removed during post-transcriptional processing.
E)   show lower efficacy if the mutation was a missense mutation that was not removed during post-translational processing and show the same efficacy if the mutation was a missense mutation, but was removed during post-transcriptional processing.

Question 10

MicroRNAs

Accepted Answer

A)   are a recently discovered mode of regulation of gene expression in Caenorhabditis elegans.
B)   are the RNA product of some regulatory genes.
C)   can bind to target mRNAs, blocking translation.
D)   are not translated into proteins.
E)   All of the answers are correct.

Question 11

Genes involved in the metabolism of an energy source are usually

Accepted Answer

A)   positively regulated.
B)   negatively regulated.
C)   not regulated.
D)   expressed constitutively.
E)   directly inhibited by ATP.

Question 12

Which of the following statements about gene expression in different cells is CORRECT?

Accepted Answer

A)   The same gene can show different patterns of expression because its position on the chromosome varies between different cells.
B)   The same gene can show different patterns because different transcription factors, enhancers and silencers may be present in different cells.
C)   Gene expression varies between cells because different cells contain different genes.
D)   The same gene can show different expression in different cells when the gene promoter region is different.
E)   If the same gene is found in different cells, it will probably show the same pattern of expression.

Question 13

You are attending a lecture in which the speaker talks about a region of DNA that includes a transcribed region as well as transcriptional regulatory sequences. Such a region must include which individual sequences?

Accepted Answer

A)   Promoter and operator
B)   Promoter, operon, ORF
C)   Promoter, TATA box
D)   Promoter and terminator only
E)   ORF, operon, terminator

Question 14

The main difference between the mode of regulation of the lac and trp operons in Escherichia coli is that

Accepted Answer

A)   the presence of tryptophan leads to the repression of the trp operon whereas the presence of lactose leads to the expression of the lac operon.
B)   the presence of tryptophan leads to the expression of the trp operon whereas the presence of lactose leads to the repression of the lac operon.
C)   the lac operon is constitutively expressed whereas the trp operon is regulated.
D)   there are no major differences in the mode of regulation, just in the products of the genes involved.
E)   the lac gene consists of a promoter region while the trp gene only contains a cis-acting operator sequence.

Question 15

The wrapping of DNA into nucleosomes hinders transcription by RNA polymerase. To allow transcription

Accepted Answer

A)   RNA polymerase in eukaryotes contains an exonuclease activity which allows the enzyme to transcribe DNA in nucleosomes.
B)   activation complexes often contain enzymes that remove acetyl groups from histones.
C)   acetyl groups are added to histone proteins, making them less positively charges and reducing the strength with which they bind to DNA.
D)   enhancer-binding proteins contain a protease to degrade histone proteins and make the DNA more accessable.
E)   a regulatory cascade ensures that transcription is coordinately regulated with the first protein product being an enzyme to remove histones from DNA.

Question 16

You are analysing a polymerase enzyme in the laboratory and discover that it cannot initiate transcription on its own. Based on this result, indicate which polymerase this is from the options provided and whether it is from a eukaryote or prokaryote.

Accepted Answer

A)   Prokaryotic DNA polymerase
B)   It could be any prokaryotic polymerase
C)   Prokaryotic RNA polymerase
D)   Eukaryotic RNA polymerase III
E)   Eukaryotic RNA polymerase II

Question 17

In what ways do enhancers and silencers involved in eukaryotic transcription differ from prokaryotic regulatory elements?

Accepted Answer

A)   Unlike eukaryotic elements, prokaryotic elements can be in any particular orientation relative to the promoter.
B)   Eukaryotic elements can be varying distances from the promoter, prokaryotic elements cannot.
C)   Prokaryotic and eukaryotic regulatory elements do not differ: they are the same in location, form and function.
D)   Prokaryotic elements can be found within introns, whereas eukaryotic elements cannot.
E)   Prokaryotic elements can 'loop', allowing them to bind to promoters. Due to the complexity of eukaryotic chromosomes, looping is not possible.

Question 18

In the presence of glucose, the lac operon

Accepted Answer

A)   is induced.
B)   is inhibited.
C)   the effect of glucose is dependent on the presence or absence of lactose.
D)   the catabolite activator protein (CAP)  binds glucose and expression is inhibited.
E)   glucose has no effect on the lac operon which is specific for lactose metabolism.

Question 19

Transcriptional control is of great importance in prokaryotes, because

Accepted Answer

A)   transcription and translation are linked.
B)   few prokaryotic mRNAs are subject to translational control.
C)   their genes are expressed a constitutive level.
D)   prokaryotic proteins do not undergo any changes after translation.
E)   prokaryotes undergo rapid environmental changes and are required to adapt.

Question 20

Gene repression is important so that

Accepted Answer

A)   genes cannot be turned off.
B)   organisms do not waste energy expressing genes that are not needed all the time.
C)   organisms can respond to their environment.
D)   genes cannot be turned off and organisms do not waste energy expressing genes that are not needed all the time.
E)   organisms do not waste energy expressing genes that are not needed all the time and organisms can respond to their environment.

Exam 12: Gene Expression