Deck 13: Regulation of Gene Expression

Question 1

A form of gene regulation that occurs while RNA is still in the nucleus is

A)differential intron removal and exon splicing.
B)feedback control.
C)enzymatic cleavage of a polypeptide.
D)rate of binding to ribosomes.

Answer 1

A

Question 2

When a bacterium is introduced to a new environment with plenty of nutritional resources,binary fission will allow for rapid growth of the population (2-4-8-16-32-64 ...etc.).However,there is usually a slight lag before the rapid growth begins.What is the best explanation for this lag period?

A)It takes time for bacterial cells to duplicate enough organelles to digest new media.
B)It takes time to induce and amplify the production of the enzymes needed for binary fission.
C)Binary fission becomes more and more efficient after each cell division.
D)The new media contains compounds that turn on repressor proteins.
E)Structural genes act more slowly than metabolic genes.

Answer 2

B

Question 3

The term "operon" comes from the Latin root word for

A)gene.
B)structure.
C)controller.
D)works.
E)copy-producing.

Answer 3

D

Question 4

Which statement is NOT correct about the trp operon?

A)The structural genes make products that are part of an anabolic pathway for the synthesis of tryptophan.
B)It is normally turned off if tryptophan is present.
C)Tryptophan acts as the corepressor.
D)Tryptophan binds to the repressor protein and inactivates it.

Question 5

Which level of primary control in eukaryotic gene activity involves changes in the polypeptide chain before it becomes functional?

A)feedback control
B)translational control
C)transcriptional control
D)posttranscriptional control
E)posttranslational control

Question 6

A deletion of one base pair that alters the sequence of codons is called a(n)

A)transposon.
B)substitution mutation.
C)carcinogen.
D)oncogene.
E)frameshift mutation.

Question 7

Which statement is NOT correct about the lac operon?

A)It regulates the production of a series of five enzymes.
B)It is normally turned off if glucose is present.
C)Lactose binds to the repressor protein and inactivates it.
D)It is an inducible system.
E)The structural genes make products that allow lactose metabolism.

Question 8

In transcriptional control in eukaryotic cells

A)a different combination of DNA-binding proteins (transcriptional factors)may regulate the activity of a particular gene.
B)enhancers may be involved in the promotion as well as regulation of gene transcription.
C)the control may be due to the phosphorylation of transcriptional factors by a kinase.
D)All of the choices are correct.
E)Only two of the choices are correct.

Question 9

In the lac operon,if lactose is present,which of the following occurs?

A)Lactose binds to the repressor,changing its shape so that it can bind to the operator and the structural genes are not expressed.
B)Lactose bind to RNA polymerase,which then binds to the promoter and transcribes the needed genes.
C)Lactose binds to the repressor,changing its shape so that it does not bind to the operator.RNA polymerase then transcribes the needed genes.
D)Lactose binds to the operon,which attracts RNA polymerase,then transcription of the needed genes occurs.

Question 10

The mRNA strand includes both introns and exons.

Question 11

Mutagens and carcinogens are associated with

A)induced mutations.
B)spontaneous mutations.
C)transposon activity.
D)None of the above.

Question 12

The level of genetic control that involves the processing of early RNA transcripts to mRNA and the rate at which mRNA leaves the nucleus is

A)feedback control.
B)translational control.
C)transcriptional control.
D)posttranscriptional control.
E)posttranslational control.

Question 13

The universal regulatory mechanism in eukaryotes for controlling gene expression includes

A)control of the genes transcribed and the rate they are transcribed.
B)control of the processing of mRNA after it is transcribed from DNA but before it leaves the nucleus,and control of the rate it leaves the nucleus.
C)control of mRNA in the cytoplasm after it leaves the nucleus,including changes to mRNA before translation begins.
D)control of polypeptides after they have been synthesized but before they are functional.
E)All of these mechanisms are used; there is no single universal mechanism.

Question 14

Active genes in eukaryotic cells are associated with

A)euchromatin.
B)heterochromatin.
C)methylated RNA and histones.
D)DNA with many methyl groups.

Question 15

"Jumping genes" that have the ability to move within and between chromosomes are called

A)introns.
B)oncogenes.
C)transposons.
D)retroviruses.
E)exons.

Question 16

Which of the following structures is not part of an operon?

A)regulator gene
B)promoter
C)operator
D)structural gene
E)All of these are part of an operon.

Question 17

Which component in an operon is incorrectly matched with its function?

A)promoter-where RNA polymerase first binds to DNA
B)regulator gene-binds to the repressor protein
C)structural gene-makes mRNA by transcription
D)operator-if not bound to the repressor,allows RNA polymerase to bind to the DNA

Question 18

The level of genetic control that involves the life span of the mRNA molecule and the ability of the mRNA to bind to ribosomes is ________ control.

A)feedback
B)translational
C)transcriptional
D)posttranscriptional
E)posttranslational

Question 19

The most critical level of eukaryotic genetic control is ________ control.

A)feedback
B)translational
C)transcriptional
D)posttranscriptional
E)posttranslational

Question 20

Which of the following is a method of posttranscriptional control?

A)transcription factors
B)the lifespan of an mRNA molecule
C)differential processing of mRNA
D)how fast the mRNA leaves the nucleus
E)Both C and D are methods of posttranscriptional control.

Question 21

Identify the major tumor suppressor gene that is more frequently mutated in human cancers than any other known gene.

A)p53 gene
B)hemoglobin gene
C)ras oncogene
D)p16
E)RB tumor-repressor gene

Question 22

Androgen insensitivity is characterized by

A)a lack of male hormones,such as testosterone.
B)external female genitalia.
C)a female karyotype.
D)the internal sex organs of a female and may bear children.

Question 23

Once proteins are functional,they are no longer subject to cellular control.

Question 24

Identify which of the operon elements plays the most critical role in determining gene regulation in prokaryotes.

Question 25

Point mutations

A)are due to a change in one DNA nucleotide.
B)may change a specific codon.
C)can cause a genetic disease such as sickle-cell disease that is due to a base change that codes for valine rather than glutamate.
D)All of the choices are correct.

Question 26

All of these are considered carcinogens EXCEPT

A)cigarette smoke.
B)ultraviolet light.
C)cabbage and related vegetables.
D)ethylene dibromide (EDB).
E)ziram,a chemical used to prevent fungal diseases on crops.

Question 27

Germ-line mutations

A)occur in sex cells.
B)can be passed to subsequent generations.
C)may range from having no effect to completely inactivating protein activity.
D)All of the answer choices are true about germ-line mutations.
E)Only two of the answer choices are true.

Question 28

All genes are active at the same time in a prokaryotic cell and controlled by positive regulation,but not in a eukaryotic cell.

Question 29

Thymine dimers

A)form when DNA is exposed to carcinogens such as tobacco smoke.
B)are rarely removed by DNA repair enzymes.
C)form when DNA is exposed to UV radiation.
D)result in abnormal protein structure which causes red blood cells to sickle.

Question 30

You are more likely to develop some form of cancer if you

A)are exposed to higher doses of radiation including X-rays.
B)are exposed to carcinogens.
C)have a high incidence of cancer in your family history.
D)All of the choices are correct.

Question 31

Explain how the actions of the lac operon are different from the trp operon.

Question 32

Compared to just a century ago,a much larger percentage of the population is living to be 80-90 years old.Why does cancer seem to be a much larger problem today than a century ago?

Question 33

________ occurs as ________ builds up in the system if Enzyme A is nonfunctional because of an inherited mutation. $\begin{array} { l }A&E_A&B&E_B&C\\\text { (phenylalanine) }&\longrightarrow&\text { (tyrosine) }&\longrightarrow&\text { (melanin) }\end{array}$

A)albinism; melanin
B)xeroderma pigmentosum; tyrosine
C)phenylketonuria; phenyalanine
D)androgen insensitivity; tyrosine

Question 34

An oncogene is

A)a viral gene with no relation to the host cell's genes.
B)a mutated form of a proto-oncogene.
C)a bacterial gene that causes cancer in the host.
D)always seen in human cancer cells.
E)a gene that turns off cellular reproduction.

Question 35

The DNA of a ________ is wrapped around histone molecules to form a "beaded string."

A)prokaryote
B)eukaryote
C)bacterium
D)All of the answer choices are correct.

Question 36

The regulator gene codes for the DNA-binding proteins that act as repressors.

Question 37

Frameshift mutations

A)most often happen when one or more nucleotides are inserted or deleted from the DNA.
B)can result in a completely new codon sequence that results in the production of non-functional proteins.
C)applies to the reading frame (sequence of codons)being changed.
D)All of the choices are correct.

Question 38

Transposons

A)are specific DNA sequences that move within and between chromosomes.
B)alter the expression of neighboring genes especially if the transposon is a regulator gene.
C)have been discovered in corn,fruit flies,bacteria,and humans.
D)All of the choices are correct.

Question 39

A change in a regulatory gene

A)must be dominant to be effective.
B)is what happens in the production of sickle-cell hemoglobin.
C)is always beneficial to the organism in which it occurs.
D)can increase or decrease the expression of a structural gene.

Question 40

A Barr body

A)exists within the cell in the form of euchromatin.
B)is an inactive Y chromosome that produces reduced amount of gene products.
C)is an inactive X chromosome that does not produce gene products.
D)exists within the cell in the form of heterochromatin.
E)Two of the above answers are correct.

Question 41

Which of the following situations would be considered an example of positive regulation of gene expression in a prokaryote?

A)The CAP protein activating the lac operon when glucose is absent and lactose is present.
B)The CAP protein activating the lac operon when lactose is absent and glucose is present.
C)The repressor protein activating the lac operon when glucose is absent and lactose is present.
D)The repressor protein activating the lac operon when lactose is absent and glucose is present.

Question 42

Which of the following problems can arise during posttranscriptional control?

A)Differential splicing of exons that can lead to an altered gene expression.
B)Incomplete excising of all introns from the pre-mRNA strand,leaving fragments to be joined with the exons.
C)Excising an exon from the pre-mRNA strand.
D)All of these are errors that can occur during posttranscriptional control of gene expression.

Question 43

The genes of a single operon are all regulated by the same repressor,operator,and promoter.

Question 44

Explain how the trp operon is regulated in a prokaryotic cell when tryptophan is present.

Question 45

In the transcription of DNA,remodeling proteins push the histone portion of the nucleosome aside so that transcription may begin.

Question 46

Which of the following series of events is associated with the formation of cancer?

A)The proto-oncogenes mutate and become oncogenes which are continuously active.There is also an associated loss of tumor suppressor gene activity allowing uncontrolled growth of cells.
B)The oncogenes mutate and become proto-oncogenes which are continuously active.There is also an associated loss of tumor suppressor gene activity allowing uncontrolled growth of cells.
C)The proto-oncogenes mutate and become oncogenes which stop functioning altogether.There is also an associated increase in the tumor suppressor gene activity allowing uncontrolled growth of cells.
D)The oncogenes mutate and become proto-oncogenes which stop functioning altogether.There is also an associated increase in the tumor suppressor gene activity allowing uncontrolled growth of cells.

Question 47

List,in order,the levels of control of gene expression in eukaryotic cells.

Question 48

One-third of all cancer deaths are due to mutations that arise from smoking tobacco.

Question 49

If CAP is absent from a cell,what are the potential consequences?

A)The individual cannot activate the catabolism of various other metabolites in the absence of glucose.
B)The individual does not have a backup system for survival when glucose is absent.
C)The individual will not be able to metabolize enough energy if glucose is absent.
D)All of these are consequences of the absence of CAP.