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MFoM > 07c: Control Of Gene Expression > Flashcards

07c: Control Of Gene Expression Flashcards

1
Q

Lac operon is present in (bacteria/mammals)

A

Bacteria

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2
Q

Lac operon is suppressed when:

A

Enough glucose in cell so it doesn’t need to use other sugars

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3
Q

The lac operon genes are (mono/poly)cistronic, which means:

A

Polycistronic; the genes for all proteins are right next to each other

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4
Q

List the order in which the genes in lack operon are present.

A
  1. Regulatory gene (i)
  2. Promoter (CRP then O)
  3. Z then Y then A genes
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5
Q

Which genes in lac operon fall under the general “operon”?

A

All except regulatory gene (i)

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6
Q

What’s the regulatory gene in lac operon? What’s its function?

A

The i gene (repressor)

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7
Q

The Z gene in lac operon codes for (X) which has what function?

A

X = beta galactosidase

Breaks down lactose to glucose and galactose

And converts lactose to allolactose

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8
Q

The Y gene in lac operon codes for (X) which has what function?

A

X = galactoside permease

Allows lactose to enter cell

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9
Q

The A gene in lac operon codes for (X) which has what function?

A

X = thiogalactoside transacetylase

Unknown function..

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10
Q

If a significant amount of glucose present in cell, what happens in terms of lac operon?

A

Repressor expressed and binds operator (RNA pol binding and transcription of lac operon blocked)

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11
Q

(X) is an isomer of lactose. What’s its role in the lac operon?

A

X = allolactose

Binds repressor, changing conformation and preventing it from binding operator

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12
Q

High glucose levels means (low/high) cAMP levels.

A

Low

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13
Q

How do cAMP levels come into play for the lac operon?

A

At very low glucose level, cAMP high and binds CRP. This complex binds promoter region of operon to stimulate high level transcription

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14
Q

Almost all transcription factors bind (X) to the (Y) groove of DNA.

A 
X = alpha helix
Y = major
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15
Q

T/F: all transcription factors act as dimers.

A

False - many do, but not all

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16
Q

T/F: the helix-turn-helix motif is found in both bacteria and euk.

A

True

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17
Q

CRP, aka (X), has which transcription factor(s)?

A

X = cAMP binding protein

Helix-turn-helix

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18
Q

Describe interaction of CRP with DNA, in terms of its motif.

A

Helix-turn-helix motif;

Recognition helix (3) interacts with major groove of DNA and is connected via turn to stabilization helix (2)

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19
Q

When CRP interacts with DNA, it acts as (monomer/dimer/multimer).

A

Dimer

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20
Q

T/F: very few transcription factors have beta sheet motifs.

A

True

21
Q

Motifs like helix-turn-helix have (strong/moderate/weak) interaction with DNA due to which bond(s)?

A

Strong interaction due to many weak hydrogen bonds

22
Q

How many molecules of Zn are used in the Zn finger motif?

A

1 or more

23
Q

What are the key residues found in Zn finger motif?

A

Repetitive motif of:

2 cys and 2 hys
OR 4 cys

With 12 AA bunch right in middle (forms finger)

24
Q

When Zn finger interacts with DNA, it acts as (monomer/dimer/multimer).

A

Multimer (can’t be dimer)

25
Q

Describe primary structure of leucine zipper.

A

35 AA stretch with leucine sticking out every 7 AA (interact to form coiled coil/zipper alpha helix

Bottom has basic region alpha helices that bind DNA

26
Q

What’s bZIP?

A

Same motif as leucine zipper, but Arg or His replace leucine

27
Q

The basic Helix-loop-helix is most similar to which other motif?

A

Leucine zipper, but there’s a non-helical loop in the zipper helix

28
Q

List steps that take place to allow estrogen to affect transcription.

A
  1. Estrogen enter cell
  2. Estrogen receptor (ER) released from HSP and bind estrogen
  3. ER-Estrogen complex enters nucleus and dimerizes with a second complex
  4. Binding of dimer to ERE (estrogen response element) on DNA
29
Q

Promoters of housekeeping genes are likely (hypo/hyper)-methylated.

A

Hypo methylated

30
Q

How do (methylated/unmethylated) CpG islands in the (X) region of the gene block expression?

A

Methylated;
X = promoter

  1. Physically preclude transcription factor recruitment
  2. MeCP2 protein binds methyl groups and prevents transcription by recruiting chromatin remodeling factors
31
Q

What’s MeCP2 and what’s its function?

A

Methyl CpG binding protein 2; binds methylated CpG islands in promoter and recruits chromatin remodeling factors (blocking gene transcription)

32
Q

T/F: methylated CpG islands in promoter always inhibit gene expression.

A

False - not always

33
Q

Igf2, aka (X), is a unique gene in that:

A

X = insulin-like growth factor 2

Imprinted gene that paternal gene (methylated) is expressed and maternal gene (unmethylated) is not

34
Q

Why is the (paternal/maternal), (methylated/unmethylated) Igf2 gene expressed?

A

Paternal; methylated

Prevents binding of a repressor

35
Q

What are methods that can impact nucleosome structure and thus gene expression?

A
  1. Positive super helical tension
  2. ATP-driven chromatin remodeling
  3. Covalent modification of Histone tails
36
Q

T/F: Chromatin remodeling requires ATP.

A

True

37
Q

Chromatin remodeling factors interact with (X) terminal of (Y) and use (Z) to (open up/close) nucleosome.

A 
X = C 
Y = RNA Pol II
Z = ATP

Open up

38
Q

Covalent modification of Histone tails includes which three processes?

A
  1. Methylation
  2. Phosphorylation
  3. Acetylation
39
Q

Which residues can be methylated on Histone tails?

A

Lys or Arg

40
Q

Which residues can be phosphorylated on Histone tails?

A

Ser

41
Q

Which residues can be acetylated on Histone tails?

A

Lys

42
Q

Which enzyme is responsible for methylation of Histone tails?

A

Histone lysine methyltransferase

Or protein Arg methyltransferase

43
Q

Covalent modification of Histone tails involves which terminus?

A

N-terminus

44
Q

Which enzyme is responsible for acetylation of Histone tails?

A

HAT (Histone acetyl transferase)

45
Q

Which enzyme is responsible for deacetylation of Histone tails?

A

HDAC (Histone deacetylase)

46
Q

Acetylation in general affects the charge on the Histone tail in which way?

A

Makes it less positively charged

47
Q

Binding of thyroid hormone to its receptor has what effect on transcription?

A

Changes HDAC domain to HAT domain, leading to acetylation and activation of transcription

48
Q

List the one Histone tail modification that represses transcription.

A

Methylation of lysine

MFoM (20 decks)

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