Deck 15: Regulation of Gene Expression

Question 1

The table below lists several genotypes associated with the lac operon in E.coli.For each,indicate with a "+" or a "-" whether ?-galactosidase would be expected to be produced at induced levels.

Answer 1

(a)- +
(b)- -
(c)+ +
(d)- -

Question 2

DNA methylation may be a significant mode of genetic regulation in eukaryotes.Methylation refers to ________.

A)altering RNA polymerase activity by methylation
B)changes in DNA-DNA hydrogen binding
C)altering translational activity,especially of highly methylated tRNAs
D)alteration of DNA polymerase activity by addition of methyl groups to glycine residues
E)addition of methyl groups to the cytosine of CG doublets

Answer 2

E

Question 3

In the diagram below,what type of control,positive or negative,is operating?

Answer 3

positive

Question 4

Compare and contrast positive and negative control of gene expression in bacteria.

Question 5

Two modular elements that appear as consensus sequences upstream from RNA polymerase II transcription start sites are ________.

A)microsatellites and transposons
B)rDNA and nucleolar organizers
C)TATA and CAAT
D)TTAA and CCTT
E)enhancers and telomeres

Question 6

Which term most appropriately refers to a regulatory protein in prokaryotes?

A)translation
B)RNA processing
C)DNA binding protein
D)gyrase action
E)helicase activation

Question 7

Which term refers to a contiguous genetic complex that is under coordinated control?

A)lysogen
B)prototroph
C)operon
D)allosteric
E)attenuation

Question 8

Which term would be applied to a regulatory condition that occurs when protein is associated with a particular section of DNA and greatly reduces transcription?

A)negative control
B)positive control
C)induction
D)activation
E)stimulation

Question 9

Which of the following terms best characterizes catabolite repression associated with the lac operon in E.coli?

A)inducible system
B)repressible system
C)negative control
D)positive control
E)constitutive

Question 10

Present an overview of prokaryotic regulation in terms of growth efficiency.

Question 11

Describe what is meant by a gratuitous inducer.Give an example.

Question 12

(a)Describe by labeled diagram the structural components of the lac operon in E.coli.
(b)State the function of the lac regulator gene.
(c)State the function of ?-galactosidase in the lac system.
(d)Show by diagram the manner in which lactose brings about transcription of the three structural genes of the lac operon.
(e)Explain why certain mutations in the regulator gene (I?)of the lac system result in maximal synthesis of ?-galactosidase,permease,and transacetylase even in the absence of the inducer (lactose).

Question 13

When referring to attenuation in regulation of the trp operon,it would be safe to say that when there are high levels of tryptophan available to the organism,________.

A)the trp operon is being transcribed at relatively high levels
B)translational termination is likely
C)transcriptional termination is likely
D)tryptophan is inactivating the repressor protein
E)ribosomes are stalling during translation of the attenuator region

Question 14

Which of the following clusters of terms applies when addressing enhancers as elements associated with eukaryotic genetic regulation?

A)cis-acting,variable orientation,variable position
B)trans-acting,fixed position,fixed orientation
C)cis-acting,fixed position,fixed orientation
D)cis-acting,variable position,fixed orientation
E)trans- and cis-acting,variable position

Question 15

Regarding eukaryotic and prokaryotic genetic regulation,what process seems to be the most similar between the two?

A)transcriptional regulation
B)RNA splicing regulation
C)intron/exon shuffling
D)5'-capping regulation
E)poly-A tail addition

Question 16

Certain mutations in the regulator gene of the lac system in E.coli result in maximal synthesis of the Lac proteins (?-galactosidase,etc.)even in the absence of the inducer (lactose).Provide an explanation for this observation.

Question 17

In the lac operon,the product of structural gene lacZ is capable of ________.

A)nonautonomous replication
B)forming lactose from two glucose molecules
C)replacing hexokinase in the early steps of glycolysis
D)splitting the ?-linkage of lactose
E)forming ATP from pyruvate

Question 18

Genetic regulation in eukaryotes can take place at a variety of levels from transcriptional to posttranslational.At what level is genetic regulation considered most likely in prokaryotes?

A)transcriptional
B)capping
C)polyadenylation of the 3' end of the mRNAs
D)intron processing
E)exon processing

Question 19

Present a detailed description of the actions of the regulatory proteins in inducible and repressible enzyme systems.

Question 20

The table below lists several genotypes associated with the lac operon in E.coli.For each,indicate with a "+" or a "-" whether functional ?-galactosidase would be expected to be produced at induced levels.

Question 21

Regarding the trp operon,trpR? maps to a considerable distance from the structural genes.The mutation either inhibits the interaction with tryptophan or inhibits repressor formation entirely.In the presence of tryptophan in the medium,would you expect the trp operon to be transcriptionally active? Explain.

Question 22

Mutations in the lacI and lacO genes of the lac regulatory system in E.coli often lead to full transcription of the three structural genes,even when no lactose is available to the organism.Such mutations would be called ________.

Question 23

Explain why lacO? mutations are cis-acting,whereas lacI mutations can be trans-acting.

Question 24

Describe the positive control exerted by the catabolite activating protein (CAP).Include a description of catabolite repression.

Question 25

What is the function of the lacY gene in the lac operon?

Question 26

A constitutive mutation in the lac operon may be of several types.Name two types of constitutive mutations.

Question 27

Monod discovered that if tryptophan is present in relatively high quantities in the growth medium,the enzymes necessary for its synthesis are repressed.How does this occur?

Question 28

Regarding regulation of the trp operon,what might one appropriately call the amino acid tryptophan?

Question 29

What experimental results would indicate that the mutation lacI? is dominant to lacI??

Question 30

Within the control region of the trp operon is a section of DNA that is sensitive to levels of tryptophan in the system.What is the name of this region?

Question 31

What is an allosteric molecule?

Question 32

What symbols are used to describe constitutive mutations at specific regions of the lac regulatory system?

Question 33

Approximately 5 percent of the cytosine residues are methylated in the genome of any given eukaryote.In what way is DNA methylation related to genetic regulation?

Question 34

What is the function of RNA interference?

Question 35

Describe the function and general nature of promoters in eukaryotes.

Question 36

The cAMP-CAP complex and RNA polymerase bind more efficiently to the lac operon together than either does alone.What term is applied to this increased efficiency of binding?

Question 37

The catabolite repression system in E.coli essentially represses the lac operon when glucose is present.What evolutionary advantage would favor evolution of such a system?

Question 38

State whether the following statement is True or false; then give your reasoning: The terminating "hairpin" loop occurs in the trp operon when sufficient tryptophan is present.

Question 39

In what way is chromosomal organization within the nucleus of an interphase cell thought to be related to gene activity?

Question 40

Name at least three different levels of regulation in eukaryotes.

Question 41

What is alternative splicing?

Question 42

Alternative RNA splicing is a method that apparently evolved for the production of many different polypeptides from the same pre-mRNA.Provide an example of alternative splicing.

Question 43

Regarding the lactose utilization system in E.coli,a gratuitous inducer is a molecule that is chemically analogous to lactose and induces the operon,but it is not a substrate for the enzymes of the lac operon.

Question 44

The enzyme permease cleaves the linkage between glucose and galactose residues in lactose.

Question 45

In what ways are eukaryotic transcription factors thought to function?

Question 46

How are siRNA and miRNAs similar?

Question 47

Name two consensus sequences or modular DNA sequences that may be found upstream from coding regions of some eukaryotic genes.

Question 48

Under a system of negative control,genetic expression occurs unless some form of regulator shuts off such expression.

Question 49

Describe how nucleosomes may influence gene transcription.

Question 50

The trp operon is typically characterized as being both under negative control and repressible.

Question 51

What type of genetic control,positive or negative,typically results when transcription factors interact with DNA?

Question 52

Describe three characteristics of enhancers.

Question 53

The lac operon consists of three structural genes as well as the adjacent region of DNA known as the regulator.

Question 54

Transcription factors appear to be important molecules relating to the regulation of gene activity.In eukaryotes,two general classes or transcription factors exist.Briefly describe each.

Question 55

What is the location of an enhancer in relation to the gene it affects?

Question 56

Regarding the lactose utilization system in E.coli,a constitutive mutant is one in which the three enzymes are produced regardless of the presence or absence of lactose.

Question 57

Mutagenic studies of the promoter region of the ?-globin gene indicate that some areas are more likely than mutations in other areas to affect transcription rates.When mutations occur in consensus sequences (modular elements such as GC box,CAAT box,TATA box),does transcription increase or decrease?

Question 58

List three different types of genetic regulation in eukaryotes.

Question 59

Under a system of positive control,transcription does not occur unless a regulator molecule directly stimulates RNA production.

Question 60

Describe the general structure of a transcription factor.

Question 61

The trp and lac operons are both subject to forms of control that are typically called negative.

Question 62

Attenuation is known to occur in the lac operon.

Question 63

In general,one could say that there are fewer levels of regulation possible in prokaryotes than in eukaryotes.

Question 64

Alternative RNA processing can result in different mRNAs that start with different exons.

Question 65

Alternative RNA processing generates different mRNAs that can direct the synthesis of different polypeptides.

Question 66

Attenuation involves the termination of mRNA synthesis.

Question 67

In the eukaryotic promoters that have it,the CAAT box appears to be critical to the promoter's ability to facilitate transcription.

Question 68

Transcription in eukaryotes is generally influenced by enhancers,just as in prokaryotes.

Question 69

Regulation of RNA transport through the nuclear membrane is as common in prokaryotes as in eukaryotes.