Deck 23: The Regulation of Gene Expression

Question 1

The trp operon in E. coli is regulated in such a manner as to allow expression of the genes only when cellular levels of tryptophan are low. When tryptophan levels are adequate, the secondary structure of the mRNA halts translation. This form of regulation is known as

A)negative regulatory control.
B)repression.
C)attenuation.
D)positive regulatory control.
E)transcriptional regulation.

Answer 1

C

Question 2

Effector molecules

A)are often small organic molecules.
B)are associated with induction of enzyme synthesis.
C)are associated with repression of enzyme synthesis.
D)induce conformational changes.
E)all of the above

Answer 2

E

Question 3

You are studying a biochemical pathway. Preliminary results suggest that this pathway is subject to end- product repression. This pathway is therefore most likely to be a(n)pathway.

A)catabolic
B)unregulated
C)constitutive
D)anabolic
E)induced

Answer 3

D

Question 4

An E.coli cell with the genotype lacOc Z+Y- A- would make which of the following protein products and in what manner?

A)Lac Z and Lac A, induced
B)Lac Y, constituitive
C)Lac Z, constituitive
D)Lac Z and Lac A, constituitive
E)Lac Z, induced

Question 5

Which of the following does NOT apply to eukaryotic gene regulation?

A)regulation as a result of compartmentalization
B)mRNA degradation (turnover)
C)protein folding
D)gene regulation by attenuation
E)protein degradation (turnover)

Question 6

The lac repressor is

A)active when glucose is present.
B)rarely active.
C)inactive when glucose is present.
D)active when both glucose and lactose are present.
E)induced when cAMP is present.

Question 7

A person with the genotype XXXY would be expected to have how many Barr bodies?

A)0
B)1
C)2
D)3
E)4

Question 8

The main chromosome of a bacterial cell possesses the following genotype with regard to the Lac operon: I- O+Z+Y- A- . This bacterial cell would

A)make LacZ independently of lactose.
B)make LacA in the presence of lactose.
C)make LacZ in the presence of lactose.
D)make no lac proteins.
E)make Lac Z and Lac Y in the presence of lactose.

Question 9

The situation in which an active regulatory protein "turns on" expression is an example of

A)feedback inhibition.
B)negative control.
C)positive control.
D)a mutation.
E)constitutive gene elements.

Question 10

Which of the following is an example of translational regulation?

A)protein degradation
B)DNA methylation
C)protein folding
D)mRNA degradation
E)DNA splicing

Question 11

Riboswitches have been observed in

A)algae.
B)prokaryotes.
C)eukaryotes.
D)yeast.
E)fungi.

Question 12

In eukaryotes, gene amplification is tolerated well when the amplified gene encodes for RNA products. However, it is rare or detrimental when the product is a protein. Why would it be advantageous for the cell to amplify the RNA- producing genes and not the protein- producing ones?

A)It allows for the manufacture of many RNA molecules when needed in the cell.
B)Proteins are amplified from a single mRNA molecule.
C)RNAs are amplified from a single protein molecule.
D)More RNA is needed by the cell than protein.
E)both A and B

Question 13

The situation in which an active regulatory protein "turns off" expression is an example of

A)positive control.
B)negative control.
C)a mutation.
D)constitutive gene elements.
E)unique regulation.

Question 14

A lac Y- mutant would

A)transport lactose into the cell effectively.
B)no longer be induced by the presence of lactose.
C)metabolize lactose.
D)not have fi galatosidase activity.
E)be constitutive.

Question 15

You are examining an enzyme associated with glycolysis. As such, you would expect

A)the protein to be expressed only during mitosis.
B)the protein to be a hormone.
C)the protein to be expressed only during development.
D)the protein to be constitutively expressed.
E)the protein to be induced by glucose.

Question 16

Sigma (a)factors can regulate the initiation of transcription. Which of the following is NOT an example of a regulation?

A)Bacteriophages may code for specific a factors that bind the core RNA polymerase and result in recognition of viral promoters.
B)There are many a sigma factors associated with eukaryotic organisms.
C)Some a factors recognize genes necessary for nitrogen utilization.
D)Some a factors recognize promoters for genes whose products are necessary when the organism is under stress, such as heat shock.

Question 17

The degradation of mRNA in the cells occurs in clusters known as

A)P bodies.
B)nuceoli.
C)iRNA sites.
D)N sites.
E)sRNA regions.

Question 18

Of the enzymes associated with the metabolism of lactose with the lac operon, the one associated with transport of lactose into the cell is

A)fi galactosidase.
B)lactose translocase.
C)transacetylase.
D)galactoside permease.
E)fi lactase.

Question 19

A male is tested for cellular abnormalities. Within each of his cells, the technician notes that there are two Barr bodies present within his cells. As a result he has the genotype

A)XO.
B)XXY.
C)XY.
D)XXXY.
E)XXX.

Question 20

Genes associated with embryonic development are known as

A)homologous genes.
B)hopanoids.
C)sigma factors.
D)homeotic genes.
E)heterologous genes.

Question 21

A bacteria has the following Lac operon genes located on the chromosome: I+P- Z+Y- A+. On a plasmid, this same bacterial cell has the lac genes I- P+Z- Y+A- . Which Lac proteins will be made? What type of protein expression will there be for each protein that is made (induced or constituitive)?

Question 22

Within a genome, an enhancer may be located

A)upstream of the gene enhanced.
B)downstream of the gene enhanced.
C)within the gene enhanced.
D)choices A, B, and C
E)both A and B

Question 23

You are working with a gene associated with an essential pathway that is necessary at two time points in an organism's lifetime. With regard to gene regulation, you would expect the gene to be

A)"activated" by particular signals (induced).
B)not constitutive.
C)"turned off" by particular signals (repressed).
D)associated with response to distinct events.
E)all of the above

Question 24

The graph below shows a growth curve of E. coli growing in a defined medium containing equal molar amounts of glucose and lactose. Based on your knowledge of the regulation of the lac operon, the best explanation of these results is that

A)the bacteria are utilizing both sugars simultaneously.
B)early on, due to the presence of lactose, the bacteria utilize the lac operon. Glucose is used later.
C)the presence of glucose causes the formation of cAMP catabolic repressor protein (CRP)complexes, which shut down the lac operon until the glucose is used up.
D)glucose is used first. Once glucose becomes limiting, intracellular cAMP increases, forming cAMP- CRP complexes that activate the lac operon to use lactose.
E)none of the above

Question 25

A transcriptional regulator that decreases transcription of a gene from a vast distance is known as a(n)

A)nonsense mutation.
B)silencer.
C)enhancer.
D)upstream control element.
E)regulator.

Question 26

DNA rearrangements in vertebrates occur in the

A)viral protein genes.
B)glycolysis genes.
C)antibody genes.
D)cell surface protein genes.
E)none of the above

Question 27

Genes that are always "turned on" in a cell are referred to as

A)inducible.
B)catabolic.
C)regulated genes.
D)constitutive.
E)mutations.

Question 28

A lacOc mutant would

A)be able to be induced by lactose.
B)never make lac structural genes.
C)have repressed expression.
D)bind receptor protein.
E)be constitutively expressed.

Question 29

The observed "puffs" in the polytene chromosomes of Drosophila are sites of

A)translation.
B)induction.
C)condensation.
D)attenuation.
E)transcription.

Question 30

One mechanism that may lead to novel disease treatment is , which hinders the translation of specific mRNAs.

A)iRNA
B)rRNA
C)siRNA
D)P bodies
E)macro- RNAs

Question 31

Inactivated X chromsomes form dark spots in the nucleus known as .

Question 32

Changes in gene expression that are not the result of changes to the gene itself are known as changes.

Question 33

A certain gene is transformed into a plant cell for potential use as a vaccine delivery system. Upon performing a Northern blot, a good deal of mRNA for the gene is produced. However, the protein product for the gene is not observed. One explanation may be that the

A)plant cell recognizes and degrades the protein in the cytoplasm.
B)mRNA is not stable in the plant cytoplasm.
C)plant ribosomes are not recognizing the mRNA translational initiation sites.
D)all of the above
E)none of the above

Question 34

Small molecules that bind directly to mRNAs and effect transcription or translation are binding to regions of the mRNA known as

A)the operator region.
B)Shine- Delgarno sequences.
C)allosteric sites.
D)ribozymes.
E)riboswitches.

Question 35

In the lac operon, Is mutations allow

A)fi- galactosidase activity, only.
B)constitutive expression of Lac proteins.
C)regulated expression of Lac proteins.
D)no expression of Lac proteins.
E)none of the above