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Alex's Genetics > Lecture 14a > Flashcards

Lecture 14a Flashcards

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Biology 101 flashcards
1
Q

What do regulatory transcription factors do?

A

They influence the level of gene expression by enhancing or inhibiting it.

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1
Q

What is transcriptional regulation?

A

When regulatory transcription factors influence the level of gene expression by inhibiting or enhancing expression.

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2
Q

In both bacteria and eukaryotes, how many ways are there to control protein activity level?

A

There are 3 ways in which the activity level of a protein is controlled.

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3
Q

What are the 3 ways in which protein activity level is controlled?

A

1) Transcriptional control
2) Translational control
3) Posttranslational control

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4
Q

What is transcriptional control? Name two examples.

A

This refers to how much RNA is being made.

The Lac Operon and the Trp operon are examples.

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5
Q

What is translational control? Name an example.

A

This refers to how heavily the mRNA is being translated.

The use of the antisense RNA to inhibit translation.

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6
Q

What are operons?

A

In bacteria, there are clusters of genes dedicated to the same biochemical pathway.

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7
Q

T/F: In an operon, the polycistronic mRNA shares regulation for all of these genes in the operon.

A

True!

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8
Q

What is polycistronic mRNA?

A

One mRNA that encodes for multiple genes/proteins.

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9
Q

In an operon, where do Shine-Delgarno sequences exist?

A

They precede the start codons of genes.

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10
Q

What are Shine-Delgarno sequences?

A

These are located on operons in bacteria and are where the ribosomes will load to translate the mRNA.

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11
Q

Does eukaryotic mRNA have Shine-Delgarno sequences? What are the exceptions?

A

Eukaryotic mRNA does NOT have Shine-Delgarno sequences EXCEPT in mitochondrial DNA/mRNA and Chloroplast DNA/mRNA.

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12
Q

What is catabolism?

A

The breakdown of a substance.

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13
Q

What do we mean when we say catabolism is inducible?

A

We only breakdown a substance for use when we need to. This is for efficiency.

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14
Q

In E. coli and other bacteria, what does the Lac Operon do?

A

It encodes 3 enzymes that catabolize lactose.

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15
Q

When Lactose is not available to be metabolized, what happens?

A

The lac operon is shut down by the lac repressor binding to the lac Operator and blocking transcriptional activation.

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16
Q

What encodes the lac repressor protein?

A

lacI

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17
Q

What does lacI do?

A

Encodes a repressor protein that binds to the operator.

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18
Q

What type of protein is the lacI protein?

A

A diffusible protein that binds to the lacO site.

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19
Q

What is the lacO site?

A

This is the lac operon operator site.

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20
Q

If a repressor protein is bound to lacO, what does this say about the presence of lactose?

A

There is NOT lactose available to be metabolized.

21
Q

Generally speaking, when is the Lac operon on?

A

The Lac operon is only on when Lactose is the most efficient carbon source available.

22
Q

What is typically the most efficient carbon source? What effect does its presence have on the Lac operon?

A

Glucose is the most efficient carbon source.

If Glucose is available, the Lac operon will be turned off.

23
Q

What happens when both lactose and glucose are available?

A

A small portion of Lactose is spontaneously converted to allolactose, which binds to the lac repressor, inactivating the repressor so it cannot bind to the operator.

24
Q

Describe the level of transcription when lactose and glucose are available.

A

There is a basal or low-level of transcription of the lac operon taking place.

25
Q

Why is there a low-level of lac operon transcription when lactose and glucose are both present?

A

The glucose is used first. The lac operon is transcribed only slightly because the CAP protein needed for high levels of transcription is inactive when CAP is by itself.

26
Q

If there is a lack of CAP binding, what does this say about glucose and lactose levels?

A

Glucose and lactose must both be present.

27
Q

What happens when there is no glucose but there is lactose?

A

The absence of glucose causes cyclic AMP (cAMP) to accumulate.

cAMP binds to the CAP protein, which forms a complex that will activate the Lac Operon as long as the Lac repressor is also absent.

28
Q

What does the cAMP-CAP complex do?

A

CAP binding enhances the binding of RNA polymerase to the promoter.

29
Q

What is the binding site for the cAMP-CAP complex called?

A

The CAP site.

30
Q

When there is a high rate of transcription, what does this say about glucose and lactose levels?

A

Glucose is absent and lactose must be present.

31
Q

What is Anabolism? Is it inducible or repressible?

A

The biosynthesis of a substance.

It is repressible meaning that the cell will keep making components unless it has enough, then it will be repressed.

32
Q

What happens when the amino acid tryptophan level is low?

A

The entire Trp operon is transcribed in order to synthesize tryptophan.

33
Q

How many enzymes does the trp operon have?

A

It includes 5 enzymes.

34
Q

What happens when the amino acid tryptophan levels are high?

A

The Trp operon will be repressed.

35
Q

Describe the mechanism for Trp operon repression.

A

The trpR gene produces a repressor trpR protein. This will bind to tryptophan to form an active complex which binds to the operator to repress it.

36
Q

What acts as the repressor and co-repressor in tryptophan repression?

A

The trpR protein is the repressor.

Tryptophan is the co-repressor.

37
Q

What is a co-repressor?

A

A small molecule that binds to a repressor, which is usually a protein.

38
Q

When will tryptophan act as a repressor?

A

Only when we have sufficient tryptophan that we don’t need to produce anymore.

39
Q

T/F: The trpR protein is active by itself.

A

False! It is inactive unless it is bound by its co-repressor, tryptophan.

40
Q

What is the most common method of genetic regulation in bacteria?

A

Predominantly at the level of transcription.

41
Q

T/F: Translational control is more common than transcriptional control.

A

False! Transcriptional control is more common than translational control.

42
Q

Describe the action of a translational regulatory protein.

A

A protein can bind outside the start codon and act as a translational repressor to prevent it from being translated.

43
Q

T/F: A translational regulatory protein can only bind to one place on the mRNA.

A

False. The protein can bind on multiple places, such as the 5’ end and start codon, to prevent translation.

44
Q

What is the Antisense RNA?

A

It is another RNA that can bind to the mRNA to prevent translation by preventing the ribosome from assembling and binding to the 5’ of the mRNA.

45
Q

What is an example of using Antisense RNA to inhibit translation?

A

Regulating the amount of water in a bacterial cell (osmoregulation).

46
Q

What produces the Antisense RNA?

A

The micF gene produces the antisense RNA.

47
Q

What does micF do?

A

Binds to the ompF RNA to prevent translation and reduce pores that bring water into the cell.

48
Q

What is an example of posttranslational regulation?

A

A common mechanism to regulate the activity of allosteric enzymes is feedback inhibition.

49
Q

What are allosteric enzymes?

A

Enzymes that can exist in different shapes to be either active or inactive.

50
Q

What is feedback inhibition?

A

This is when the final product will go back and inhibit the first enzyme by binding to the regulatory site.

51
Q

What are the sites in an allosteric enzyme? What enzyme in the feedback loop would this be?

A

It has a catalytic and regulatory site to be either active or inactive. Enzyme 1 is an allosteric enzyme.

Alex's Genetics (38 decks)

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