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gedical menetics > jean exzprezion > Flashcards

jean exzprezion Flashcards

1
Q

What are housekeeping genes

A

genes are expressed in all cells at constant levels

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2
Q

What can expression of non housekeeping genes depend on

A

on tissue, developmental stage and intra/extracellular signals (e.g. hormones

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3
Q

What does changing gene expression do to Polymerase

A

changes ability of RNA polymerase to bind promoter

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4
Q

How is bacterial transcription initiated

A

nding of sigma factor to promoter, which enables RNA polymerase to bind to promoter to form preinitiation complex

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5
Q

What determines is sigma factor binds promoter

A
  • Complementarity to promoter region
  • Type of sigma factor
  • Repressor/activator protein (affect ability of RNA polymerase to bind to promoter, because prokaryotic DNA is naked.)
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6
Q

How is bacterial DNA organised

A

organised into operons – sets of genes under control of one promoter (e.g. lac operon)

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7
Q

Are there operons in eukaryotic DNA

A

No

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8
Q

Describe structure of operon

A

contain regulatory DNA sequences (e.g. promoter) that control transcription of the operon, sequences are binding sites for regulatory proteins, which control how much the operon is transcribed

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9
Q

Describe 2 regulatory proteins that control gene expression

A

Repressor

Activator

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10
Q

What does repressor do

A
  • Binds to DNA section called operator

- reduces transcription (e.g., by blocking RNA polymerase from moving forward on the DNA

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11
Q

What does activator do in bacterior

A

bound to its DNA binding site, it increases transcription of the operon

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12
Q

How does chromatin contribute to controlling gene expression of genes

A

Not all DNA readily accessible, some genes constitutively repressed.

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13
Q

Effect of DNA methylation, give example

A

Chromatin more compact and less accessible. TSGs often silenced in cancer cells by hypermethylation.

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14
Q

What happens in DNA methylation

A

: metyhtransferase converts cytosine to 5-cytosine, methyl group disrupts binding of proteins needed for transcription

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15
Q

Describe structure of heterochromatin

A

more condensed due to methylation

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16
Q

Describe structure of euchromatin, and its effect on DNA structure

A

. Lysine residues of histone tails acetylated . Acetylation can neutralise the positive charge of the histone tail ,so -ve charged DNA less tightly wrapped around histone/nucleosome and more accessible

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17
Q

What can euchromatin recruit because of DNA being less tightly wound

A

chromatin remodelling complexes (shift nucleosomes and induce conformational changes in chromatin) and TATA box binding protein associated factors (which recruit other factors for transcription)

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18
Q

What are core promoters

A

regions in front of genes allowing polymerase to recognise beginning of gene.

19
Q

What does RNA polymerase need to associate promoter sequence

A

General transcription factor

20
Q

How do GTFs work

A
  • GTF recognises specific sequences – i.e. the promoters, binds promoter sequence creates scaffold then correct polymerase is recruited onto a protein scaffold
21
Q

Does polymerase recognise promoter itself

A

NO

22
Q

How can specific polymerase get recruited to promoter

A

Each promoter recognised by different subtype of GTF #

23
Q

What is combinatorial control

A

many TFs work together, recruit proteins to form transcriptional complex at promoter allowing RNA pol to bind

24
Q

Does RNA polymerase recognise DNA sequence itself in bacteria

A

Yes

25
Q

How can TF act in a trans manner

A
  • recruit other regulatory proteins expressed by the cell.
  • These complexes bind to the gene and increase accessibility of initiating site to RNA polymerase. -can affect genes far away in genome.
26
Q

what is TATA sequence

A
  • TATA box is a sequence of DNA found in the core promoter region
  • TATA binding protein binds, initiates formation of basal transcription complex.
27
Q

What do activators and coactivators ensure

A

correct and regulated expression of genes – in response to tissue specific and proliferation cues.

28
Q

Where do activators and coactivators bind

A

regions outside the core promoter elements.

29
Q

What are TFs

A

• Proteins that bind to promoters or other regulatory DNA regions to increase/decrease gene expression

30
Q

Describe distal regulatory elements position and role

A
  • contribute to regulation of activation of gene
  • regions can be megabases away, trans acting TFs alter transcription of distant genes, by binding far away from core promoter (e.g. in distal regulatory elements) through DNA protein and protien protein interactions
31
Q

How can enhancers activate promoter region that is far away

A

associate with protein (same TF as promoter), protein can grab DNA, fold It by protein protein interactions forming loops – brings certain regions of DNA closer together, allows enhancer and promoter to interact
- , activate transcription complex on promoter allows RNA polymerase to transcribe

32
Q

What does silencer do

A

Switch off promoter, negative effect on transcription

33
Q

What does insulator do

A

only activates promoter to right not left, limits how enhancer affects gene expression.

34
Q

What are the components of distal regulatory elements

A

Locus controlling region
Insulator
Silencer
Enhancer

35
Q

Example of extracellular substance that controls gene expression

A

Hormone

36
Q

How can hormone regulate gene expression

A
  • Lipid soluble hormone diffuses into cells binding to receptors inside cells, hormone receptor complex diffuse into nucleus binding to receptor elements in DNA
37
Q

How are some TFs cis acting

A

bind promoter regions: GC box, CAAT box, TATA box

acting on gene immediately following promoter region

38
Q

Describe eukaryotic promoter region

A

core promoter, proximal promoter and distal regulatory elements/distal promoter. The DNA has the capability to fold back on itself. This also explains the fact that, the effect of many regulatory sequences take place even though they are located many kilobases away from the site of transcription

39
Q

Why is TATA box important promoter element

A

binding of transcription factor proteins to the TATA box assists in the binding of RNA polymerase, which then results in the formation of transcription complex.

40
Q

How can TATA box be inhibited

A

This process will be inhibited when histone proteins get bound to the TATA box.

41
Q

How in transcription achieved in eukaryotes

A
  • promoter that involves in transcription is identified by sigma factor.
  • Each single sigma factor would recognize a single core promoter sequence
  • Both RNA polymerase and the sigma factor collectively identify the correct promoter region and form the transcription complex.
42
Q

What is core promoter

A

minimal portion of the promoter required to properly initiate transcription

43
Q

What do core promoter, proximal and distal regulatory elements contain

A

transcription factor binding sites

44
Q

What is needed before RNA polymerase can work in eukaryotic cells

A

transcription factor and its associated transcription mediator complex must be attached to a DNA binding site called a promoter region

gedical menetics (2 decks)

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