module 7 lec 10

Question 1

What type of operon is the Trp operon?

Answer 1

It is a repressible operon.

Question 2

What is the role of the Trp operon?

Answer 2

The Trp operon regulates the synthesis of the amino acid tryptophan in bacteria.

Question 3

How is the Trp operon typically regulated?

Answer 3

The Trp operon is repressed when tryptophan is abundant. The repressor binds to the operator to stop transcription.

Question 4

What happens when tryptophan levels are low in the cell

Answer 4

The Trp operon is active, and genes for tryptophan synthesis are transcribed.

Question 5

What molecule activates the repressor in the Trp operon?

Answer 5

Tryptophan acts as a corepressor by binding to the repressor, activating it to bind to the operator.

Question 6

What does TrpR refer to in the Trp operon?

Answer 6

TrpR is the repressor gene that regulates the Trp operon.

Question 7

How does TrpR+ affect Trp operon repression when tryptophan is present?

Answer 7

TrpR+ allows repression of the Trp operon in the presence of tryptophan (repressor binds to operator, stopping transcription).

Question 8

What happens in the absence of tryptophan with TrpR+?

Answer 8

TrpR+ results in no repression, allowing transcription of the operon and production of tryptophan.

Question 9

What is the role of TrpR- in the Trp operon?

Answer 9

TrpR- is a nonfunctional repressor that cannot bind to the operator, resulting in constitutive expression of the operon regardless of tryptophan levels

Question 10

What happens when TrpR- is present and tryptophan is available?

Answer 10

Even with tryptophan, TrpR- cannot repress the operon, leading to high levels of tryptophan synthesis.

Question 11

What is the difference in repression between TrpR+ and TrpR-?

Answer 11

TrpR+ represses the operon in the presence of tryptophan (low transcription), while TrpR- results in constant transcription regardless of tryptophan (high transcription).

Question 12

What is attenuation in the context of the Trp operon?

Answer 12

Attenuation is a mechanism where the availability of charged tRNA (with tryptophan) controls the production of full-length mRNA.

Question 13

How does tRNA charged with tryptophan affect Trp operon transcription?

Answer 13

: When tRNA is charged with tryptophan, it allows attenuation to occur, causing premature termination of transcription and thus preventing full-length mRNA production.

Question 14

What happens if there is low tryptophan or low charged tRNA?

Answer 14

If tryptophan is low, attenuation does not occur, allowing full-length mRNA to be synthesized and the operon to be transcribed.

Question 15

What role does tRNA play in Trp operon attenuation?

Answer 15

tRNA charged with tryptophan affects the formation of a hairpin loop in the mRNA, which regulates whether transcription continues or terminates prematurely.

Question 16

What is the connection between attenuation and the Trp operon?

Answer 16

Attenuation in the Trp operon is a regulatory mechanism that controls gene expression based on the availability of charged tRNA and tryptophan levels.

Question 17

How does the Trp operon use attenuation to regulate gene expression?

Answer 17

The Trp operon uses attenuation to prevent unnecessary synthesis of tryptophan by halting transcription when tryptophan is abundant (via charged tRNA).

Question 18

What are regulons?

Answer 18

Regulons are groups of operons regulated by the same regulatory proteins, often in response to environmental changes or stress.

Question 19

What is an example of a regulon in E. coli?

Answer 19

An example of a regulon in E. coli is the heat shock response, where several genes are activated to deal with heat-induced stress

Question 20

How does E. coli respond to high temperature through a regulon?

Answer 20

At high temperatures, E. coli induces proteins that degrade damaged proteins and help refold proteins using molecular chaperones.

Question 21

What mediates the heat shock response in E. coli?

Answer 21

The heat shock response in E. coli is mediated by special sigma factors that control the expression of stress response genes.

Question 22

What is the role of sigma factors in regulons?

Answer 22

Sigma factors direct RNA polymerase to specific promoters, enabling the expression of genes involved in stress responses, like the heat shock regulon.

Question 23

How are operons and regulons related?

Answer 23

Regulons consist of multiple operons that are regulated together by the same regulatory proteins, typically in response to a specific environmental signal.

Question 24

sigma 32 and 70 do what

Answer 24

recognize promoter sequence for heat shock response

Question 25

at high twmpweatures sigma 24 recognizes different promoter sequences on _____ gene and _____ is transcribed

Answer 25

rPOH; sigma 32

Question 26

What are small RNAs (sRNAs)?

Answer 26

Small RNAs (sRNAs) are short RNA molecules that regulate gene expression by interacting with mRNA to inhibit or activate translation.

Question 27

How do sRNAs usually inhibit translation?

Answer 27

sRNAs typically inhibit translation by base-pairing with the ribosome binding site (RBS) of the mRNA, preventing ribosome attachment

Question 28

Can sRNAs activate translation?

Answer 28

Yes, sRNAs can activate translation by disrupting stem-loop structures in the mRNA, making the ribosome binding site accessible.

Question 29

What other effect can sRNAs have on mRNA?

Answer 29

Some sRNAs lead to mRNA degradation, either by promoting degradation directly or by affecting the stability of the mRNA.

Question 30

How do sRNAs typically work?

Answer 30

sRNAs usually work by base-pairing with complementary regions of the mRNA, either blocking translation or promoting mRNA degradation.

Question 31

What is one mechanism by which sRNAs can activate gene expression

Answer 31

sRNAs can activate gene expression by disrupting secondary structures (like stem-loops) in mRNA, freeing up the ribosome binding site for translation.

Question 32

Are sRNAs involved in mRNA degradation?

Answer 32

Yes, some sRNAs can lead to mRNA degradation, often by recruiting ribonucleases to cleave the mRNA.

Question 33

Are sRNAs involved in prokaryotic gene regulation?

Answer 33

Yes, sRNAs play a key role in prokaryotic gene regulation by influencing translation and mRNA stability.

Question 34

What is antisense RNA?

Answer 34

Antisense RNA is RNA transcribed from the strand of DNA opposite the template strand, which is complementary to the mRNA.

Question 35

How does antisense RNA inhibit translation?

Answer 35

Antisense RNA can inhibit translation by base pairing with the sense strand of mRNA, preventing ribosome binding or translation initiation.

Question 36

Can antisense RNA lead to mRNA degradation?

Answer 36

Yes, antisense RNA can lead to mRNA degradation by forming double-stranded RNA, which is recognized by RNases for cleavage.

Question 37

How can antisense RNA affect transcription

Answer 37

Antisense RNA may interfere with the transcription of the sense gene by base pairing with the mRNA, preventing transcription elongation or initiation.

Question 38

What is the general mechanism of antisense RNA in gene regulation?

Answer 38

Antisense RNA regulates gene expression by base pairing with the sense mRNA, either inhibiting translation, promoting degradation, or blocking transcription.

Question 39

What is the relationship between sense and antisense RNA?

Answer 39

Sense RNA is the mRNA produced by transcription of the gene’s coding strand, while antisense RNA is the complementary RNA transcribed from the opposite strand, which can regulate gene expression.

Question 40

Can antisense RNA inhibit both translation and transcription?

Answer 40

Yes, antisense RNA can inhibit both translation (by base-pairing with mRNA) and transcription (by interfering with gene transcription).