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BIOL 311 > Chapter 10 > Flashcards

Chapter 10 Flashcards

1
Q

In prokaryotes what is the relationship between transcription and translation?

A

They occur simulataneously

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2
Q

What is the difference between RNA polymerase in eukaryotes and prokaryotes?

A

In prokaryotes there is only 1 while in eukaryotes there are 3 RNA polymerases.

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3
Q

What is RNA polymerase made up of?

A

A 5-subunit core plus a subunit called a sigma factor.

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4
Q

What does the sigma factor do?

A

It positions the RNA polymerase at the right spote at the promoter.

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5
Q

What is the factor independent termination?

A

When the GC rich DNA is followed by a stretch of A rich DNA the RnA polymwerase detaches from the DNA.

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6
Q

What is the rho-dependent termination?

A

The Rho factor (protein) recognizes a C rich sequence on the DNA and then releases RNA polymerase from the DNA template.

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7
Q

What are the 3 methods of gene regulation in bacteria?

A

1.) Bacteria need to acquire and breakdown sugars from the environment.
2.) Bacteria conserve energy by only making the enzymes required for import and metabolism when that particular sugar is present.
3.) Bacteria recognize environmental conditions and then respond to them by activating/repressing particular genes

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8
Q

What is the promoter?

A

This is the DNA sequence where the RNA polymerase binds to initiate transcription.

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9
Q

What is an activator?

A

Protein bringing the RNA polymerase closer to the promoter.

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10
Q

What is a repressor?

A

Protein blocking RNA polymerase from binding to the promoter or blocking it from moving along the DNA.

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11
Q

How can the RNA polymerase be repressed?

A

Either it does not bind or it binds but cannot move.

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12
Q

What is the allosteric effector?

A

This is a small molecule that binds to the allosteric site of a regulatory protein and some regulatory proteins can bind to the activator binding site when there is an effector and some can bind when there is no effector.

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13
Q

What does the effector do?

A

The presence or absence of the effector helps the cell to respond to the environmental conditions.

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14
Q

In lactose metabolism what is the effector?

A

Lactose prevents the repressor from bbinding

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15
Q

What is the sign for negative regulation?

A

Repressor

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16
Q

What is the sign for positive regulation?

A

Activator

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17
Q

What is an operon?

A

This is when multiple genes are transcribed onto a single mRNA molecule, they are functionally related genes, and are controlled by a single promoter.

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18
Q

What is the lac operon?

A

This is the DNA that contains genes which when read lead to the synthesis of enzymes that breakdown the lactose.

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19
Q

What does the Y gene do?

A

It is used to make permease which transports lactose into the cell.

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20
Q

What does the Z gene do?

A

It is used to make the B-galactosidase which modifies the lactose into allolactose and can then be metabilized.

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21
Q

What does the I gene do?

A

It encodes the repressor protein.

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22
Q

Is the I gene part of the lac operon?

A

No

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23
Q

What are trans-acting genes?

A

These are genes that affect gene expression of distant genes on DNA other than where the trans acting factor is encoding.

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24
Q

What are cis-acting genes?

A

These affect gene expression of nearby gens that are on the same piece of DNA.

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25
Q

What happens when there is no lactose present?

A

lac operon turns OFF

26
Q

What happens when the lactose is present?

A

This is known as induction and the lac operon is ON.

27
Q

What is a merozygote?

A

This is when there is a partial diploid because the bacteria contains its own DNA and then an F’ plasmid which makes it a partial diploid.

28
Q

Which is dominant for Z?

A

Z+ is dominant over Z-

29
Q

Which is dominnat for Y?

A

Y+ is dominant over Y-

30
Q

What happens in P-?

A

The RNA polymerase cannot bind to the promoter.

31
Q

What is dominant for P?

A

P+ is dominant over P-

32
Q

What is Oc?

A

This is the consituitive operator where the repressor cannot bind.

33
Q

What happens when Oc is present?

A

In a noninductive or inductive operon there is always expression of Y and Z.

34
Q

What does non-inductive mean?

A

Lactose is not present

35
Q

What does induction mean?

A

Lactose is present

36
Q

Which components are cis-acting?

A

O and P

37
Q

Which components are trans-acting?

A

I

38
Q

What is the similarity between I- and Oc?

A

They are both constituitive

39
Q

Which is dominant in I?

A

I+ > I-

40
Q

What is Is?

A

This is the super repressor which affects the allosteric site and the inducer (allolactose) cannot bind Is is always in the DNA binding form.

41
Q

Including Is was is the dominant order of I?

A

Is > I+ > I-

42
Q

What is stronger Oc or Is?

A

Oc is more powerful

43
Q

Why is Oc stronger than Is?

A

This is because the Is makes a repressor which can bind to the operator in the absence of the inducer, but the repressor cannot bind to an altered operator such as Oc its the exception.

44
Q

Which is preferred glucose or lactose?

A

Glucose is preferred to lactose because it is easily broken down by comparison and is energy efficient.

45
Q

When is lactose or another carbon source used?

A

When glucose has been entirely used up.

46
Q

What happens to the lac operon in the presence of glucose?

A

There is minimal expression.

47
Q

What happens to the lac operon in the absence of glucose?

A

There is maximum or enhanced expression

48
Q

How does the lac operon know that the glucose levels are low?

A

ATP is turned into a protein called cAMP and when there are high glucose levels and cAMP levels are low the lac operon has less expression, however, when the glucose levels are low the cAMP levels are high the lac operon expression is high.

49
Q

What is cAMP?

A

It is the allosteric effector for CAP.

50
Q

What is CAP?

A

It is the activator protein that binds to the CAP binding site in the promoter.

51
Q

What is the CAP-cAMP complex?

A

Activates transcription by RNA polymerase.

52
Q

When is the Trp operon turned on?

A

When there is low or no tryptophan present in the environment.

53
Q

What happens when Trp is present?

A

The Trp binds to the repressor as an allosteric effector and causes inhibition of transcription.

54
Q

What happens when Trp is absent?

A

The repressor cannot bind to the operator and the Trp operon is transcribed.

55
Q

What happens when there is low or no tryptophan in the environment?

A

The Trp operon is on.

56
Q

What is attenuation?

A

When the mRNA production is decreased due to Trp abundance.

57
Q

What does the leader sequence do?

A

Synthesizes the Trp amino acid.

58
Q

What happens when the Trp levels are high?

A

The tRNAs are sufficient with tryptophan and lead to translation.

59
Q

What happens when the Trp levels are low?

A

The ribosome stalls at the trp codons in the leader peptide.

60
Q

How does termination occur?

A

The RNA polymerase transcribes the stem loop which is followed by a string of U’s .

BIOL 311 (12 decks)

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