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Fundamentals of the Living Cell > Intro to gene expression control > Flashcards

Intro to gene expression control Flashcards

Understand: - levels of gene expression control (ex: thalassaemia) - translational control - regulation of RNA stability by microRNAs

1
Q

How is differential gene expression regulated in time? [2 marks]

A
  • Embryonic gene expression differs from gene expression in adults
  • It differs in response to hormones, infections and other signals
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2
Q

How is differental gene expression regulated in space? [1 mark]

A

Different tissues/cell types express different genes

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3
Q

What happens if genes for metabolism are not tightly regulated? [1 mark]

A

Metabolic diseases (e.g. diabetes mellitus) can arise

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4
Q

What happens if genes for cell shape/mobility are not tightly regulated? [2 marks]

A
  • Cells may move faster or to other tissues

- This can cause cancer metastasis

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5
Q

What happens if genes for cell regulation are not tightly regulated? [1 mark]

A

Congential diseases can arise

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6
Q

What happens if genes for cell proliferation are not tightly regulated? [3 marks]

A
  • Cells can go through the cycle faster
  • Cells can skip checkpoints
  • Causing cancer
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7
Q

What is the bithorax complex? [3 marks]

A
  • Group of homoeotic genes in Drosophila melanogaster
  • Controls the differentiation of the thorax
  • Mutations cause drosophila to have 2 thoraxes, wings and stomachs
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8
Q

What is antennapedia?

A
  • Gene that controls the formation of legs

- Mutation causes legs instead of antenna to form at the front

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9
Q

What are totipotent cells? [2 marks]

A
  • Can produce all cell types

- Both somatic cells and extra-embryonic parts (e.g. placenta, membrane)

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10
Q

What are pluripotent cells? [1 mark]

A
  • Can produce several functional cell types (e.g. bone marrow stem cells)
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11
Q

How to reprogram cells back to pluripotent cells? [1 mark]

A

Add transcription factors

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12
Q

Post transcriptional regulatory steps [5 marks]

A
  • Capping
  • Polyadenylation
  • Splicing
  • Nuclear transport
  • Translation
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13
Q

What happens if there is a mutation in the promoter region? [1 mark]

A

The gene can’t be expressed

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14
Q

What happens if there is a mutation in the intron? [2 marks]

A
  • It cannot be spliced by the spliceosome

- A specific sequence in the intron must be recognised by the spliceosome

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15
Q

When does gene expression in embryos occur and how? [2 marks]

A
  • At the end of blastocyst formation

- Due to up-regulation of translation from maternal pre formed mRNA

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16
Q

Environmental stresses that control translation? [2 marks]

A
  • Heat shock

- Pathogens

17
Q

First codon in frame [1 mark]

A

AUG

18
Q

What is the Kozak sequence? [2 marks]

A
  • Sequence in 5’ UTR

- Guides ribosome to the first AUG after it

19
Q

What does the preinitiation complex contain? [4 marks]

A
  • Small ribosomal subunit (40S)
  • eIF1
  • eIF2-Met-tRNAi-GTP complex
  • eIF3
20
Q

What is the function of eIF3 [2 marks]

A
  • Associates with 40S subunit

- Binds near E site

21
Q

What is the function of eIF2? [3 marks]

A
  • Associates with Met-tRNAi and GTP
  • Combines to form 48S subunit
  • Binds near P site
22
Q

What is the function of eIF1? [2 marks]

A
  • Binds to 40S subunit to stabilise “open” confirmation of the preinitiation complex
  • Binds near A site
23
Q

What regulates the efficiency of translation? [3 marks]

A
  • eIF3
  • eIF4
  • Cap
24
Q

Function of ferritin and its gene expression [3 marks]

A
  • Binds to excess iron
  • Retains it in the cytoplasm as a store
  • Translated very poorly
25
Q

Ferritin mRNA in low iron [3 marks]

A
  • 5’ UTR forms a loop
  • Ribosome can’t go past loop
  • Loop recognised by iron starvation inhibitor
26
Q

Ferritin mRNA in high iron [4 marks]

A
  • Iron binds to inhibitor
  • Inhibitor leaves mRNA
  • Ribosome undoes loop
  • Translation is fast
27
Q

What are micro RNAs (miRNAs)? [4 marks]

A
  • Small non coding RNAs
  • Regulate post transcriptional regulation of almost 1/3 of human genes
  • Usually by blocking translation of selective mRNAs
  • One miRNA can regulate several target genes
28
Q

What are miRNAs made from and how? [2 marks]

A
  • Cytolytic enzymes cleave off ends and signal peptide of precursor miRNA
  • Short dsRNA molecule recognised by RNA Induced Silencing Complexes (RISC)
29
Q

What does RISC do afterwards? [2 marks}

A
  • RISC binds and unwinds RNA molecule

- RISC forms complex with antiparallel strand

30
Q

Extensive match v. less extensive match

A

Extensive = mRNA is rapidly degraded and RISC is released

Less extensive = Ribosome is stopped, mRNA is sequestered and then degraded

Fundamentals of the Living Cell (35 decks)

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