14-Regulation of Bacterial Gene Transcription

-,-,+,+

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease I+P+O+Z+Y+ Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma)

-,-,+,-

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease I+P+O+Z+Y- Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma, use "n" for N/A)

-,+,+,+

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease I+P+O+Z+Y-/F'I+P+O+Z-Y+ Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma, use "n" for N/A)

-,-,-,-

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease I+P-O+Z+Y+ Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma)

+,+,+,+

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease I-P+O+Z+Y+ Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma)

-,n,+,n

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease I-Z+/I+Z- Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma, use "n" for N/A)

-,n,+,n

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease I-Z-/I+Z+ Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma, use "n" for N/A)

-,-,-,-,

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease IsP+O+Z+Y+/F'I+P+O+Z+Y+ Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma, use "n" for N/A)

-,n,+,n

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease O+Z+/OcZ- Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma, use "n" for N/A)

+,n,+,n

-IPTG B-gal, -IPTG permease, +IPTG B-gal, +IPTG permease O+Z-/OcZ+ Consider the above strain. A partial diploid is indicated by the symbol, /; all sequences to the left of the /are on the E. coli genome, and the sequences to the right of the / are on a different DNA molecule. The F+symbol means that the other dnA molecule is a plasmid called the fertility or F plasmid. the strains are grown in the absence of glucose and lactose. complete the chart using + to indicate the presence of enzyme activity (B-galactosidase and/or permease), and - to indicate its absence depending on the addition of IPTG to the medium. (separate symbols by a comma, use "n" for N/A)

C

Attenuation of the trp operon: a. Occurs when transcription is complete before translation begins b. Is mediated by the trp repressor protein c. Occurs in the presence of high levels of tryptophan

A

Bacteria use these enzymes to degrade mRNA: a. RNases b. phosphatases c. proteases d. core RNA polymerase

C

Catabolite-sensitive operons cannot be induced if ____ is present. a. lactose b. galactose c. glucose d. cAMP-CRP

A

E. coli uses ____________ in preference to lactose a. glucose b. fructose c. succinate d. mannose

B

Genes within an operon: a. tend to be regulated by a separate and different regulatory mechanisms. b. Are generally involved in the same biochemical pathway. c. Are expressed as a polydactylous RNA.

A

If transcription proceeds without pausing, what stem loop structures are formed in the trpL mRNA? a. 1-2 and 3-4 b. 1-3 only c. 2-4 only d. 1-3 and 2-4

terminator

In bacterial cells, transcription and translation occur simultaneously. RNA polymerase will begin transcribing the trp mRNA until it reaches the leader sequence. Here, a ribosome begins translating the leader sequence starting at its AUG codon. When the ribosome gets to the sequences for the two trptophans, it pauses because it has to wait for trptophan (it isn't readily available because it is present in a low concentration.) This pause in the ribosome's movement affects the mRNA's secondary structure. Since the tryptophan codons are on segment 1 of the leader sequence, 1 cannot bind 2, thereby freeing 2 to bind 3 (forming the antiterminator.) Since 2 is bound to 3, 3 cannot bind to 4 to form the __________. Therefore, RNA polymerase continues transcribing the entire operon.

B

In negative regulation, a(n) _____ turns of the transcription of one or more genes. a. activator b. repressor c. enhancer d. regulon

A

In positive regulation, a(n) _____ activates a promoter. a. activator b. repressor c. enhancer d. regulon

3 (three)

In the lambda phage, P(R) is the right promoter and P(L) is the left promoter. P(R) is regulated by O(R), the right operator region containing three operators, and P(L) is regulated by O(L), the left operator region which also contains three operators.

C

Negative _____ occurs because the gene product regulates its own synthesis. a. repression b. activation c. autoregulation d. catabolite repression

T

T/F: A gene which is usually turned down but can be activated is under negative control.

T

T/F: A polycistronic mRNA is transcribed from the lac operon when lactose is present and glucose is absent in the E. coli cell.

F

T/F: All of the genes involved in control and functioning of the lac operon are inducible.

T

T/F: Bacterial mRNA may be monocistronic or polycistronic.

F

T/F: Bacterial mRNA usually has a long lifespan compared to other kinds of bacterial RNA.

F

T/F: If regions 1 and 2, and 3 and 4, of the trpL mRNA form stem loops, the trpE gene will be transcribed.

T

T/F: If regulation of a gene involves a repressor protein, it is an inducible gene.

T

T/F: It is rare to have two adjacent tryptophan codons because normally tryptophan accounts for only 1% of amino acids residues in a protein.

T

T/F: The cro protein and lambda repressor proteins bind to the same sites within OR

T

T/F: The process of attenuation in the trp operon turns off the operon when it is not needed by the cell.

T

T/F: The tryptophan operon is regulated at the levels of transcription initation, elongation, and termination.

T

T/F: the lac repressor protein is active in the absence of lactose within the cell.

operator

The DNA sequence components of the trp operon include promoter, ________, leader (with attenuator), trpE, trpD, trpC, trpB, trpA.

C

The E. coli _____ gene godes for B-galactosidase. a. lacA b. lacY c. lacZ d. lacE

trp operon

The ______ codes for three enzymes that are essential for tryptophan (an amino acid) synthesis.

attenuation

The _______ of tryptophan depends on the secondary structure of the mRNA (formation of the 3-4 haripin)

A

The __________ complex binds to an activator site upstream from the lac promoter and activates lac operon transcription. a. cAMP-CRP b. ATP c. allolactose d. enhancer

allolactose

The binding of a repressor is never infinitely strong. Sometiems (meaning approximately once a generation) the protein will come loose and RNA polymerase will be able to transcribe the gene. This is called the basal level of transcription. With this basal level, permease (all one to two molecules of it) is available to bring lactose into the cell and B-galactosidase (again, all one to two molecules of it) is available to convert a small amount of lactose into ______. Then _______ binds to the repressor, causing its conformation to change so that it falls off the operator. RNA polymerase can then freely transcribe the lac genes making the lac enzymes much more readily available.

B

The inducer for the lac operon is: a. lactose b. allolactose c. B-galactosidase d. galactose

B

The lac repressor binds to what site within the lac operon? a. LacZ b. lacO c. lacA d. lacI e. lacP

E

The lac repressor is inactivated by binding to which of the following? a. lactose b. betagalactosidase c. transcription factors d. glucose e. allolactose

A

The most convincing evidence that lacI is a diffusible protein is: a. A partial diploid with only one functional lacI gene is able to regulate both copies of the lac operon. b. A partial diploid with only one functional lacO is unable to regulate both copies of the lac operon. c. The lacI gene is located very close to the lac operon. d. Mutants lacking lacI function do not respond to changes in lactose concentration.

D

The segment of mRNA that codes for a polypeptide chain is called a(n): a. translation unit b. promoter unit c. operon d. open reading frame.

CI

The way in which ____ binds to O(L) and O(R) in the lambda phage determines whether it enters the lytic or lysogenic state.

+

Using + (present) or - (absent) as symbols, indicate the elvel of B-galactosidase expected in wild-type E coli exposed experimentally to the following treatment protocol: + lactose, -cAMP

+

Using + (present) or - (absent) as symbols, indicate the elvel of B-galactosidase expected in wild-type E coli exposed experimentally to the following treatment protocol: +lactose, +cAMP

-

Using + (present) or - (absent) as symbols, indicate the elvel of B-galactosidase expected in wild-type E coli exposed experimentally to the following treatment protocol: -Lactose -cAMP

-

Using + (present) or - (absent) as symbols, indicate the elvel of B-galactosidase expected in wild-type E coli exposed experimentally to the following treatment protocol: -lactose, +cAMP

D

What is the best explanation for the stem loop arrangement seen in the absence of translation of the trpL gene? a. region 4 binds to region 3 before region 2 has been transcribed b. Region 1 is unable to bind to region 3 or 4 c. The 1:2 stem loop has more base pairs than a 2:3 stem loop d. The ribosome prevents region 1 from binding to any other region.

C

Which of the following elements, when nonfunctional, would lead to a reduction in the total amount of functional lacZ produced by a bacterial cell? a. The operator b. The lacI gene c. The CAP site d. The lacA gene e. The lacY gene

B

Which of the following genes is not a structural gene of the lac operon: a. lacA b. lacI c. lacY d. lacZ

D

Which of the following is not part of the lac operon? a. lacO b. lacZ c. lacA d. lacI e. lacP

B

Which of the following occurs if tryptophan levels are high? a. regions 2 and 3 form a stem loop structure b. regions 3 and 4 form a stem loop structure c. regions 1 and 4 form a stem loop structure d. no stem loop structures are formed

A

Which of the following would you expect to find in an inducible system? a. A repressor protein, which is bound to DNA in absence of any other factor b. A repressor protein, which is bound to DNA in the presence of a corepressor c. An activator protein, which is bound ot DNA in absence of any other factor. d. An activator protein, which is bound to DNA only in the absence of an inhibitor.

A

Why does the ribosome stall on region 1 during attenuation? a. Translation of this region requires trp-tRNA b. High levels of tryptophan interfere with ribosome function c. Low levels of tryptophan lead to intrinsic termination d. Binding of the repressor protein prevents further translation

C

______ is a true inducer of the lactose operon. a. B-galactosidase b. Glucose c. Allolactose d. ATP

glucose

_______ is invovled in the inhibition of phosphorylation of adenylate cyclase which prevents cAMP formation. With no cAMP, the cAMP-CRP complex cannot form and therfore cannot bind to its activator site upstream from the promoter to activate synthesis. Another way ______ can slow lac operon expression is by acting through an inducer exclusion mechanism. In this mechanism, a product of _____ (EIIA) binds to lactose permease (the product of the lacY gene), which inactivates it. This prevents lactose from entering the cell and being converted into allolactose. With no allolactose, the repressor protein will remain bound to the operator.

polycistronic

_______ mRNAs enconde multiple proteins. (Often they are in a specific metabolic pathway. When they are all together, their synthesis is regulated coordinately, and a single signal will cause similar quantities of related proteins to be produced at the same time.

lac operon

the ________ codes for B-galactosidase, which metabolizes lactose into glucose and galactose, permease, which helps lactose to enter the cell, and B-galactoside transacetylase, which has an unknown function.