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Cells, organisms and systems > 3.5 - Control of gene expression > Flashcards

3.5 - Control of gene expression Flashcards

1
Q

what does it mean when a gene is expressed?

A

turned on, making protein associated to said gene

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2
Q

when do genes expressed and proteins produced vary? (3)

A
  1. cell type
  2. developmental stage
  3. environmental conditions
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3
Q

housekeeping genes

A

constitutively (constantly) expressed genes, code for proteins performing basic cell functions

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4
Q

what is the main way or regulating gene expression?

A

controlling transcription

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5
Q

transcription factors

A

proteins that bind to DNA, effecting frequency of transcription of specific gene therefore associated protein

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6
Q

how is gene expression in bacteria highly efficient?

A

genes only expressed when/where they’re required

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7
Q

promoters (2)

A
  1. genes have upstream control elements in DNA (promoters)
  2. in absence of regulation, promoter exhibits basal (base level) level of transcription
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8
Q

repressors

A

binds to promoter blocking RNA polymerase

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9
Q

activators

A

stimulate RNA polymerase binding to promoter (bind slightly upstream from promoter)

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10
Q

operons

A

used in bacterial gene expression, gene cluster and promoter plus additional sequences, function together in regulation

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11
Q

2 eukaryotic transcription factor domains (2)

A
  1. DNA-binding domain
  2. activation domain
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12
Q

DNA-binding domain (2)

A
  1. binds to regulatory sequences
  2. transcription factor proteins structures so they can interact with major groove of DNA helix to affect gene transcription
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13
Q

activation domain

A

regulates polymerase through binding other proteins

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14
Q

3 main types of eukaryotic transcription factor (3)

A
  1. homeodomain DNA-binding unit
  2. zinc finger domains
  3. leucine zipper
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15
Q

promoter positive and negative regulatory elements (3)

A

positive:
1. enhancer
negative:
1. silencers
2. insulators

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16
Q

enhancer elements (promoter regulatory element) location

A

typically thousands of base pairs away from transcription start site (different thing to promoter). either upstream (5’), downstream (3’) or within an intron of transcribed sequence

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17
Q

silencers and insulators (promoter regulatory elements) role (3)

A
  • distant
  • repress transcription
  • demarcate (set boundaries) of regulatory unit/prevent the regulatory sequences within affecting adjacent cells
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18
Q

how can enhancer function be assayed

A

by fusing reporter gene (such as green fluorescent protein) to gene of interest

19
Q

enhancer (promoter element) role

A

bind transcription factors and co-activators that help stabilise transcription machinery making it easier for RNA polymerase to initiate transcription.

20
Q

how does chromatin effect RNA polymerase access to promoters

A

hinders access to promoters (default repression)

21
Q

what is required for RNA polymerase to access promoter?

A

chromatin remodelling

22
Q

what is required for even base level of gene expression?

A

positive regulation mechanisms

23
Q

how is transcription precision maintained in eukaryotes

A

combinatorial control of many different factors such as enhancers, chromatin remodelling and basal transcription factors

24
Q

examples of transcription factor activation (2)

A
  1. steroid hormone (hydrophobic)
  2. hormone (hydrophilic)
25
Q

steroid hormone transcription factor activation (3)

A
  1. hydrophobic
  2. pass through cell membrane and bind to receptor in cytoplasm
  3. receptors translocate to nucleus, acts as transcription factors to directly regulate gene expression
26
Q

hormone transcription factor activation (3)

A
  1. binds to receptor on cell membrane
  2. activates protein kinase
  3. kinase phosphorylates specific inactive transcription factor activating it, triggers activation of particular gene
27
Q

heterochromatin

A

dense, inactive regions of chromosome

28
Q

euchromatin

A

less dense, active regions of chromosome (allows access to transcriptional machinery)

29
Q

remodelling complexes

A

condense/recondense chromatin by sliding nucleosomes in chromosome (allows/prevents access to transcriptional machinery)

30
Q

what allows the recruitment of enzymes and transcription factors?

A

reversible covalent modification, mostly at N-terminus domain (amino) - found near exterior of nucleosome

31
Q

how can histones be modified (3)

A
  1. acetylation
  2. phosphorylation
  3. methylation (can be heritable - epigenetic)
32
Q

protein synthesis control points in eukaryotes (7)

A
  1. synthesis of primary RNA transcript
  2. posttranscriptional modifications of mRNA
  3. degradation of mRNA
  4. protein synthesis
  5. posttranslational modification of protein
  6. targeting and transport of protein
  7. degradation of protein
33
Q

role of alternative splicing in perception of different sound frequencies (4)

A
  1. sound vibrations activate potassium channels in hair cell membranes
  2. need 100s of different channel isoforms (different versions) to respond to different frequencies
  3. alternative exons used at 8 regions encode >500 isoforms of channels
  4. each responds to different sound frequency
34
Q

microRNA role

A

RNAs that regulate eukaryotic gene expression by binding to mRNAs

35
Q

how to microRNAs regulate gene expression (3)

A
  1. binds to mRNA
  2. larger initial transcript cleaved to yield the mature mRNA, associates with proteins of argonaut family to form complexes
  3. microRNA component of complex binds to mRNA (base pair formation), mRNA subsequently degraded (by cleaving it or blocking translation)
36
Q

% human genes regulated by microRNA

A

60%

37
Q

proteasome

A

big complex of enzymes, recycles proteins in eukaryotes

38
Q

how do proteasomes degrade/recycle proteins? (2)

A
  1. proteins targeted for breakdown by labelling with ubiquitin
  2. resulting amino acids can be re-used in biosynthesis or further broken down to carbon skeletons for other uses
39
Q

stages of protein life cycle (7)

A
  1. transcription initiation
  2. posttranscriptional processing
  3. RNA stability
  4. translational regulation
  5. protein modification
  6. protein transport
  7. protein degradation
40
Q

what phase of protein do drugs mostly target?

A

complete proteins eg. receptors and enzymes

41
Q

when are most genes expressed in life cycle of a differentiated tissue?

A

early development

42
Q

how can you induce pluripotent stem cells? (2)

A
  1. isolate (eg skin cell - fibroblast) and grow in culture
  2. introduce genes for a cocktail of transcription factors into the cell
43
Q

potential applications for induced pluripotent stem cells? (3)

A
  1. tissue replacement
  2. studying diseases
  3. drug screening
44
Q

what cells can become any type of cell?

A

inner mass cells of early embryos

Cells, organisms and systems (25 decks)

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