module 7 lec 8

Question 1

Why is gene regulation necessary?

Answer 1

Gene regulation ensures that genes are expressed at the right time, in the right cells, and at appropriate levels, allowing for cellular function and adaptation.

Question 2

Where can gene regulation occur in protein production?

Answer 2

Gene regulation can occur at several stages:

Transcriptional
Posttranscriptional
Translational
Posttranslational

Question 3

What is transcriptional regulation?

Answer 3

Transcriptional regulation controls the initiation of transcription, determining whether a gene is transcribed into mRNA.

Question 4

What is posttranscriptional regulation?

Answer 4

Posttranscriptional regulation controls the processing of mRNA, including splicing, capping, and export from the nucleus.

Question 5

What is translational regulation?

Answer 5

Translational regulation controls the initiation of translation, determining whether mRNA is translated into a protein.

Question 6

What is posttranslational regulation?

Answer 6

: Posttranslational regulation modifies the activity or location of a protein after translation, including processes like phosphorylation or protein degradation.

Question 7

What is the preferred carbon source for Escherichia coli?

Answer 7

Escherichia coli prefers glucose as its carbon source.

Question 8

What happens when glucose is depleted and only lactose is available to E. coli?

Answer 8

When glucose is depleted, E. coli can metabolize lactose, and the genes for lactose metabolism are induced.

Question 9

What is induction in the context of E. coli and lactose metabolism?

Answer 9

Induction is the process where genes for lactose metabolism are switched on when lactose is available as the sole carbon source.

Question 10

How can induction of lactose metabolism be observed?

Answer 10

Induction can be observed by looking at the diauxic growth curve, which shows two growth phases: one with glucose and another with lactose.

Question 11

What does a diauxic growth curve look like in E. coli?

Answer 11

The diauxic growth curve shows two phases of growth: one during glucose metabolism and another after glucose is depleted and lactose metabolism begins.

Question 12

Who discovered the Operon Model of gene regulation?

Answer 12

Francois Jacob, Jacques Monod, and Arthur Pardee.

Question 13

What did Jacob, Monod, and Pardee discover about E. coli and lactose metabolism?

Answer 13

They found that lacZ and lacY genes are essential for lactose metabolism, while lacA is not essential.

Question 14

What is the role of the lacZ and lacY genes in E. coli?

Answer 14

lacZ and lacY are required for the metabolism of lactose.

Question 15

Where are the lacZ, lacY, and lacA genes located in E. coli?

Answer 15

They are located next to each other on the bacterial chromosome.

Question 16

What is the function of the lacZ gene in E. coli?

Answer 16

lacZ encodes β-galactosidase, which breaks down lactose into glucose and galactose.

Question 17

What is the function of the lacY gene in E. coli?

Answer 17

lacY encodes lactose permease, a protein that transports lactose into the cell.

Question 18

What happens if the lacZ or lacY gene is mutated in E. coli?

Answer 18

E. coli cannot metabolize lactose properly without functional lacZ or lacY.

Question 19

What is constitutive expression in the context of the lac operon?

Answer 19

Constitutive expression means the genes are always on and continuously expressed.

Question 20

What caused constitutive expression in lac operon mutants

Answer 20

Mutations in the lacI gene prevented regulation of gene expression.

Question 21

What does the lacI gene encode?

Answer 21

lacI encodes a repressor protein that controls the expression of the lac operon.

Question 22

What is the role of the lacI gene in regulating the lac operon?

Answer 22

The lacI gene produces a repressor that binds to the operator, blocking transcription unless lactose is present.

Question 23

What is the function of the lacI gene?

Answer 23

lacI encodes the repressor protein that regulates the lac operon.

Question 24

How does the lacI repressor control the lac operon?

Answer 24

The repressor binds to the operator region, preventing RNA polymerase from transcribing the lac genes.

Question 25

How is the lacI repressor turned off?

Answer 25

Lactose (or allolactose) binds to the repressor, causing it to change shape and release from the operator, allowing transcription.

Question 26

What happens when lactose is absent in the lac operon system?

Answer 26

The lacI repressor binds to the operator, blocking transcription and preventing lactose metabolism.

Question 27

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

Answer 27

A mutated lacI gene can cause constitutive expression of the lac operon, even when lactose is not present.

Question 28

What is repression in gene regulation?

Answer 28

Repression is the process where gene expression is turned off or reduced.

Question 29

How does a repressor control gene expression?

Answer 29

A repressor protein binds to the operator region of a gene, blocking RNA polymerase from initiating transcription.

Question 30

What is negative regulation in gene expression

Answer 30

Negative regulation occurs when a repressor prevents gene expression by blocking transcription.

Question 31

What is an example of repression in the lac operon?

Answer 31

In the lac operon, the lacI repressor binds to the operator when lactose is absent, preventing transcription of lac genes.

Question 32

How can repression be relieved in the lac operon?

Answer 32

When lactose is present, it binds to the repressor, causing it to release from the operator, allowing transcription to occur.

Question 33

What is induction in gene regulation?

Answer 33

Induction is the process where gene expression is turned on or increased in response to a specific signal.

Question 34

How does induction work in the lac operon?

Answer 34

Induction occurs when lactose binds to the lacI repressor, causing it to release from the operator, allowing transcription of the lac genes.

Question 35

What role does lactose play in induction of the lac operon?

Answer 35

Lactose (or its isomer allolactose) acts as an inducer by binding to the lacI repressor, preventing it from blocking transcription.

Question 36

What happens when lactose is absent in the lac operon?

Answer 36

Without lactose, the lacI repressor binds to the operator, blocking transcription and preventing lactose metabolism.

Question 37

What is the difference between induction and repression in gene expression?

Answer 37

Induction increases gene expression, while repression decreases or prevents gene expression.

Question 38

What happens to the lac operon when lactose is absent in the medium?

Answer 38

lacI produces a repressor that binds to the operator, preventing gene expression.

Question 39

How does the presence of lactose affect the lac operon?

Answer 39

Lactose binds to the repressor, causing it to release from the operator and allowing gene expression to begin.

Question 40

What is an inducible operon?

Answer 40

An inducible operon, like the lac operon, is usually off but can be turned on (induced) when a specific molecule (like lactose) is present.

Question 41

What role does the lacI gene play in the regulation of the lac operon?

Answer 41

lacI encodes the repressor protein that binds to the operator and blocks transcription unless lactose is present

Question 42

What happens when lactose binds to the lacI repressor?

Answer 42

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