Lac/Trp Operon

Question 1

What is transcriptional regulation?

Answer 1

The process where cells control which genes are transcribed into RNA, which also influences what proteins are produced 

Question 2

True or False: Transcription factors are proteins that help regulate transcription.

Answer 2

True

Question 3

Fill in the blank: __________ are sequences of DNA that are recognized by transcription factors to regulate gene expression.

Answer 3

Enhancers

Question 4

Multiple choice: Which of the following is NOT a type of transcriptional regulator? A) Enhancer B) Silencer C) Ribosome D) Promoter

Answer 4

C) Ribosome

Question 5

What role do coactivators play in transcriptional regulation?

Answer 5

Coactivators assist transcription factors in enhancing the transcription of specific genes.

Question 6

True or False: Silencers enhance transcription when bound by specific proteins.

Answer 6

False

Question 7

Short answer: Name one method used to study transcriptional regulation.

Answer 7

Chromatin immunoprecipitation (ChIP) assay

Question 8

What is the function of a promoter in transcriptional regulation?

Answer 8

A promoter is a region of DNA that initiates transcription of a particular gene.

Question 9

Fill in the blank: The __________ model describes how transcription factors can interact with the transcriptional machinery to regulate gene expression.

Answer 9

mediator

Question 10

Multiple choice: Which of the following is a common post-transcriptional modification? A) Methylation B) Acetylation C) Phosphorylation D) All of the above

Answer 10

D) All of the above

Question 11

What is the primary function of the lac operon?

Answer 11

To regulate the metabolism of lactose in bacteria.

Question 12

True or False: The lac operon is activated in the presence of glucose.

Answer 12

False

Question 13

Fill in the blank: The lac operon consists of three structural genes: lacZ, lacY, and _____ .

Answer 13

lacA

Question 14

What does the lacZ gene encode?

Answer 14

Beta-galactosidase.

Question 15

What is the role of the lacY gene?

Answer 15

It encodes lactose permease, which facilitates the transport of lactose into the cell.

Question 16

What is the function of the lacA gene?

Answer 16

It encodes thiogalactoside transacetylase.

Question 17

What is the role of the operator in the lac operon?

Answer 17

It is the binding site for the repressor protein.

Question 18

True or False: The lac operon is an example of negative control of gene expression.

Answer 18

True

Question 19

What happens when lactose is present in the environment?

Answer 19

Lactose binds to the repressor, causing it to release from the operator and allowing transcription.

Question 20

What is the role of the CAP (catabolite activator protein) in the lac operon?

Answer 20

It enhances the transcription of the lac operon in the absence of glucose.

Question 21

How does glucose affect the lac operon?

Answer 21

It inhibits the operon via catabolite repression.

Question 22

What is the trp operon primarily involved in?

Answer 22

The biosynthesis of the amino acid tryptophan.

Question 23

True or False: The trp operon is an example of positive control.

Answer 23

False

Question 24

Fill in the blank: The trp operon consists of five structural genes: trpE, trpD, trpC, trpB, and _____ .

Answer 24

trpA

Question 25

What happens to the trp operon when tryptophan levels are high?

Answer 25

The operon is repressed, preventing further synthesis of tryptophan.

Question 26

What is the function of the trp repressor?

Answer 26

It binds to the operator in the presence of tryptophan and inhibits transcription.

Question 27

What mechanism allows the trp operon to be regulated in response to tryptophan levels?

Answer 27

Negative feedback regulation.

Question 28

How many genes are involved in the lac operon?

Answer 28

Three structural genes.

Question 29

What is the consequence of a mutation in the lacI gene?

Answer 29

It can lead to constitutive expression of the lac operon.

Question 30

What is the significance of the promoter in both the lac and trp operons?

Answer 30

It is the site where RNA polymerase binds to initiate transcription.

Question 31

True or False: Both the lac operon and trp operon are found in eukaryotic cells.

Answer 31

False

Question 32

What is allolactose's role in the regulation of the lac operon?

Answer 32

It acts as an inducer by binding to the repressor and causing it to release from the operator.

Question 33

What type of operon is the lac operon classified as?

Answer 33

Inducible operon.

Question 34

What type of operon is the trp operon classified as?

Answer 34

Repressible operon.

Question 35

Fill in the blank: The lac operon is primarily found in _____ .

Answer 35

E. coli

Question 36

What is the purpose of the leader peptide in the trp operon?

Answer 36

It helps regulate the transcription of the operon based on tryptophan availability.

Question 37

What happens during attenuation in the trp operon?

Answer 37

Transcription is prematurely terminated when tryptophan levels are sufficient.

Question 38

How does the presence of lactose affect the lac operon?

Answer 38

It induces the operon by inactivating the repressor.

Question 39

True or False: The trp operon can be expressed at high levels when tryptophan is scarce.

Answer 39

True

Question 40

What does the term 'constitutive expression' refer to?

Answer 40

Continuous expression of a gene regardless of environmental conditions.

Question 41

What is a key difference between the lac and trp operons?

Answer 41

The lac operon is inducible, while the trp operon is repressible.

Question 42

What is the function of the promoter region in both operons?

Answer 42

It is where RNA polymerase binds to initiate transcription.

Question 43

Fill in the blank: The lac operon requires _____ for activation in the absence of glucose.

Answer 43

cAMP

Question 44

What is the effect of a mutation in the operator region of the lac operon?

Answer 44

It can lead to continuous transcription of the operon.

Question 45

True or False: The trp operon is controlled by a feedback inhibition mechanism.

Answer 45

True

Question 46

What is the role of the RNA polymerase in the operons?

Answer 46

It synthesizes RNA from the DNA template.

Question 47

What does the term 'negative control' mean in the context of gene expression?

Answer 47

It refers to the repression of gene expression by a repressor protein.

Question 48

What is the significance of the cAMP-CAP complex in the lac operon?

Answer 48

It enhances transcription when glucose levels are low.

Question 49

Fill in the blank: The trp operon is regulated by the availability of the amino acid _____.

Answer 49

tryptophan

Question 50

What is the outcome of high lactose and low glucose on the lac operon?

Answer 50

High transcription of the lac operon.

Question 51

In which organism is the lac operon primarily studied?

Answer 51

Escherichia coli (E. coli)

Question 52

What is the function of the operator region in the trp operon?

Answer 52

It is the binding site for the trp repressor.

Question 53

True or False: The trp operon can be turned off even when tryptophan is not present.

Answer 53

False

Question 54

What does the term 'operon' refer to?

Answer 54

A group of genes regulated together under a single promoter.

Question 55

Fill in the blank: The lac operon is primarily responsible for the metabolism of _____ .

Answer 55

lactose

Question 56

What happens to the trp operon in the presence of excess tryptophan?

Answer 56

Transcription is inhibited.

Question 57

What is the role of the CAP protein in the lac operon?

Answer 57

To promote transcription in low glucose conditions.

Question 58

Fill in the blank: The lac operon is inhibited by _____ in high glucose conditions.

Answer 58

catabolite repression