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Drew 912 > Block 4 -- Regulation of Gene Expression > Flashcards

Block 4 -- Regulation of Gene Expression Flashcards

1
Q

What is the purpose of gene expression regulation?

A

1) energy conservation
2) environmental adaptation
3) regulation of development & differentiation

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2
Q

What are the 2 control sites?

A

Promoter

Operator

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3
Q

What does the z gene encode in the lac operon?

A

beta-galactosidase

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4
Q

Function of beta-galactosidase?

A

lactose –> glucose + galactose

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5
Q

What does the y gene encode in the lac operon?

A

galactosidase permease

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6
Q

What is the function of galactosidase permease?

A

allows entry of lactose into cell

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7
Q

What does the a gene encode in the lac operon?

A

Thiogalactosidase transacetylase

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8
Q

What is the function of thiogalactosidase transacetylase?

A

not sure!

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9
Q

What gene encodes the repressor in the lac operon?

A

lac i

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10
Q

What is the inducer in the lac operon?

A

allolactose

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11
Q

What is the function of the regulator gene in the lac operon?

A

encodes the trans-acting factor

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12
Q

define polycistronic mRNA.

A

mRNA that encodes for many proteins, present in eukaryotes

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13
Q

Where does CRP/cAMP complex bind?

A

regulatory region of promoter

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14
Q

What is the function of CRP/cAMP?

A

stimulate the binding of RNAP by bending DNA to provide an additional site for RNAP interaction

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15
Q

what does CRP/CAP stand for?

A
    • cAMP repressor protein

- - catabolite activator protein

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16
Q

Why is glucose preferred by prokaryotes?

A

It is the normal carbon source for amino acids, although lactose may be used

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17
Q

If LacI repressor and CRP/cAMP are both present, what happens?

A

No transcription

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18
Q

What does the trp operon encode?

A

Enzymes for—

chorismate –> tryptophan

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19
Q

What concepts of gene regulation does the trp Operon use?

A

1) co-repression

2) attenuation

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20
Q

What concepts of gene regulation does the lac operon use?

A

Catabolite repression

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21
Q

What are the components in co-repression for trp operon?

A

1) repressor

2) co-repressor = trp

22
Q

What is the function of the co-repression complex in the trp operon?

A

Works to reduce transcription rate

23
Q

Describe the structure of the trp operon.

A

1) trpR
2) Control (P, O)
3) trpL
4) trpE, D, C, B, A

24
Q

What does trpR encode?

A

The repressor protein

25
Q

What is the function of the leader?

A

encodes an mRNA leader that controls whether operon is transcribed (includes attenuator)

26
Q

What domains pair under low trp levels? High?

A

Low–2&3

High–3-4 (Rho-independent RNAP termination)

27
Q

Define attenuation.

A

The interruption of transcription

28
Q

What is heterochromatin?

A

Nonexpressed DNA (e.g. X chromosome in female mammals)

29
Q

What is euchromatin?

A

Transcriptionally active DNA

30
Q

What are types of gene expression controls in DNA?

A

1) G/C methylation to silence the TATA box
2) Gene loss or amplification
3) Gene rearrangement

31
Q

Describe deregulation at the DNA level.

A

Gene rearrangement (e.g. B cell recombination)

32
Q

What DNA sequences encode for a variable antibody chain?

A

1 D_H, V_H, J_H

33
Q

What regions are present on trans-acting factors?

A

1) DNA binding domain

2) Activation domain

34
Q

What is the function of the DNA binding domain in a trans-acting factor?

A

recognition of DNA sequence

35
Q

What motif(s) are present in the DNA binding domain of trans-acting factors

A

1) Zn fingers

2) Helix-turn-helix

36
Q

What is the function of the activation domain in a trans-acting factor?

A

Allows assembly of transcription complex at the TATA box.

37
Q

What motif(s) are present in the activation domain of trans-acting factors?

A

1) Leucine Zippers

38
Q

Where are Zinc fingers commonly found?

A

in the DNA binding domain of steroid hormone receptors

39
Q

Describe the structure of the Zn finger motif.

A
    • 2 cysteines + 2 histidines chelated to a Zn ion
    • 20 residue repeat
    • each looks like a finger
40
Q

Describe the structure of the leucine zipper motif.

A
    • Dimerized helices via hydrophobic interactions form a coiled coil
    • 30-40 residue alpha-helix
    • Leu every 7th residue
    • Portion of dimer grips DNA at basic residues
41
Q

How do gene-specific activating proteins work?

A

1) bind DNA
- —-or——
2) are co-activating proteins with enzymatic activity
- - eg histone (de)acetylase
- - bind trans-acting factors

42
Q

How do steroid hormones & growth factors increase transcription rate of certain genes?

A

2nd messenger system

    • cAMP
    • kinases pass signal from membrane to nucleus
43
Q

Define epigenetic regulation.

A

Regulation of gene expression without changing DNA sequence

44
Q

What are methods of epigenetic regulation?

A

1) Cytosine methylation in CpG islands

2) Histone methylation & acetylation

45
Q

How does methylation of cytosines in CpG islands work, and when is it important?

A

Reduce transcription

    • globin genes in non-RBCs
    • gene expression in development
46
Q

Does histone methylation increase or reduce transcription rate?

A

reduce

47
Q

What is an example of post-transcriptional processing?

A

B Apoliprotein (liver & intestinal isoforms)

    • component of lipoproteins
    • intestinal is longer (C –> U)
    • Stop codon formed
48
Q

What are types of post-transcriptional processing?

A

1) RNA editing

2) mRNA transport

49
Q

Functions of miRNA?

A

bind dsDNA to tag for degradation

inhibit translation

50
Q

What is the function of the 3’ Poly(A) tail?

A

Increase stability of mRNA

– reduce effect of nuclease attack

51
Q

How is mRNA protected during transport?

A

bound to proteins to prevent nuclease degradation

52
Q

How does the transferrin receptor up-regulate when [Fe] is low?

A
    • IRE-BP binds hairpin loop of mRNA for the receptor at 3’ end
    • Prevents degradation
    • Higher affinity when [Fe] is low

Drew 912 (4 decks)

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