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Genes: Organisation and Function > L12 Eukaryotic Transcription > Flashcards

L12 Eukaryotic Transcription Flashcards

1
Q

Eukaryotic Cell

A
  • has a nuclear membrane

- poses a problem during transcription and translation as mRNA needs to be transported from the nucleus

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2
Q

Genome size - paradox

A

More DNA doesn’t necessarily mean more genes

Size of genome doesn’t reflect number of genes you have

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3
Q

DNA during mitosis

A

See OneNote image

  • highly compact DNA and protein, not easily transcribed
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4
Q

DNA during interphase

A

See OneNote image

  • strands of chromatin
  • DNA state where expression occurs
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5
Q

Chromatin

A
  • composed of DNA and proteins: histones and non-histone proteins
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6
Q

Nuclear structure

A

See OneNote diagram

  • nucleolus = where ribosomal RNA is made

DNA is not free flowing in nucleus, there are specific domains e.g. peripheral heterochromatin

Location in the nucleus and its correlation to expression/no expression

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7
Q

Nuclear localisation

A

See OneNote diagram

Expressed genes tends to be towards the middle

Non-expressed genes tends to be near the periphery

Nuclear localisation is not absolute

Localisation happens naturally for some genes or endogenous mechanism that control their location

E.g.
if in repressive domain: tether genes to periphery => not expressed

if in activating domain: regardless of where it is located, always expressed

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8
Q

Exome

A

Exome = all coding material in that chromosome, translated into proteins

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9
Q

Genome size

A

Factors influencing genome size:

  1. gene density (intergenic regions)
  2. introns (size and number)
  3. repeats
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10
Q

RNA polymerases

A
  • DNA dependent RNA polymerase
  • 3 types in eukaryotes
  • core components are homologous with prokaryotic RNA pol except for the sigma factors
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11
Q

Genes transcribed by RNA pol 1,2,3

A

See OneNote table

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12
Q

Types of RNA

A

See OneNote table

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13
Q

Prokaryotic vs Eukaryotic genes

A

See OneNote diagram

Prokaryotic mRNA:
Polycistronic, codes for more than one protein
Operons that are co-regulated by 1 TF

Eukaryotic mRNA:
Encodes 1 protein
Protein has modified 5’ end and modified 3’ end
Intron splicing

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14
Q

Eukaryotic mRNA processing

A

5’ capping
RNA splicing
3’ polyadenylation

Export
Translation

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15
Q

Primary RNA transcript

A

See OneNote diagram

Encodes protein that does a generalised function?

After it mRNA has been translated, has slightly different domains and functions in different cells

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16
Q

Gene Organisation - Drosophila Adh region

A

See OneNote diagram

  • osp (outspread wings) mutations mapped to both side of Adh
  • Adh, Adhr, two other genes within introns of osp

Osp gene sits in the intron of the Adh genes
Can have entire genes sitting inside introns

Adh region has multiple start sites, polyA sites and differential splicing

17
Q

RNA polymerase - conserved subunits of bacterial and eukaryotic RNA polymerases

A

See OneNote table

18
Q

Transcription

A
  • RNA pol 2 transcribes protein coding genes (mRNA)

Steps in transcription at Class 2 (RNA pol 2) promoters

  1. formation of pre-initiation complex
  2. promoter melting: separation of 2 DNA strands
  3. initiation: formation of the first phosphodiester bond in the nascent (freshly generated) mRNA
  4. promoter clearance
  5. elongation
  6. termination
19
Q

Transcription initiation

A

See OneNote diagram

Inr = transcription initiation point

  • which promoter present is dependent on the gene
  • each promoter contains a subset of these elements e.g. TATA and Inr
20
Q

Some genes lack apparent core promoter elements

A
  • e.g. lack TATA, Inr, DPE
  • these genes often transcribed at low rates
  • are housekeeping genes
  • have multiple transcription start points, not as specific (facilitate regulator gene expression, not as specific)
  • contain CG-rich sequences (CpG islands)
21
Q

Promoter Recognition

A

General transcription factor TF2D:

  • TATA binding protein (TBP)
  • TBP associated factors (TAFs)
  • binds core promoter elements and initiates assembly of pre-initiation complex (TF2D, TF and RNA pol 2) on the promoter

Has motif that recognises TATA sequence

TAF2 recognises Inr sequences

Different components of TF2D recognises different sequences in the promoter => any combination of the interaction can lead to transcription initiation

22
Q

Pre-initiation complex

A

TF2D, TF and RNA pol 2

23
Q

TF2D

A

See OneNote diagram

  • can be recruited by different promoter elements
  • for each promoter, the”initiating” interaction between the promoter and TF2D may differ depending on the specific sequence of the elements
24
Q

Transcription initiation - additional GTF

A

See OneNote diagram

GTF = general transcription factors
- in addition to TF2D, other GTFs required

Genes: Organisation and Function (33 decks)

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