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BIOL5014 - Molecular Biology > Control of gene expression > Flashcards

Control of gene expression Flashcards

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1
Q

What is transcription selectivity?

A

Transcription selectivity is the process by which only a subset of genes is transcribed at any given time.

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2
Q

What is the term for the set of genes transcribed at any one time in any one tissue?

A

The term for the set of genes transcribed at any one time in any one tissue is the transcriptome.

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3
Q

What is the relevance of transcription selectivity to disease and development?

A
  • different cell types transcribe different sets of genes, and this gives each cell type its unique identity.
  • Changes in transcription selectivity can lead to disease, and researchers can study transcriptomes to identify genes that are important for specific biological processes.
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4
Q

Where is RNA polymerase found?

A

RNA polymerase is found in all cells, from bacteria to humans.

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17
Q

What are the subunits of RNA polymerase?

A

RNA polymerase is made up of multiple subunits. The number of subunits varies depending on the type of organism.

For example, bacterial RNA polymerase has four subunits, while eukaryotic RNA polymerase II has twelve subunits.

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17
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17
Q

What is the reaction that RNA polymerase catalyzes?

A

RNA polymerase catalyzes the following reaction:
DNA + NTPs → RNA + NDPs + PPi

NTPs = nucleoside triphosphates (ATP, GTP, CTP, and UTP)
NDPs = nucleoside diphosphates (ADP, GDP, CDP, and UDP)
PPi = pyrophosphate

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21
Q

Are any of the subunits of RNA polymerase homologous between prokaryotes and eukaryotes?

A

Yes, some of the subunits of RNA polymerase are homologous between prokaryotes and eukaryotes. This means that they evolved from a common ancestor.

For example, the β subunit of bacterial RNA polymerase is homologous to the Rpb1 subunit of eukaryotic RNA polymerase II.

21
Q

What are the different subunits?

A
  • β’- and β-like
  • α-like
  • ω-like
  • Enzyme-specific subunits
  • Common subunits
21
Q

What are the types of polymerase in eukaryotes?

A
  • Pol I
  • Pol II
  • Pol III
  • Prokaryote polymerase
21
Q

Pol I

A

Eukaryotic RNA polymerase I, which transcribes ribosomal RNA genes.

22
Q

Do the three types of RNA polymerase share any subunits?

Pol I/II/III

A

Yes

22
Q

Pol III

A

Eukaryotic RNA polymerase III, which transcribes transfer RNA genes, 5S ribosomal RNA genes, and other small RNAs.

22
Q

Prokaryote polymerase

A

Bacterial RNA polymerase, which transcribes all genes in the bacterial genome.

22
Q

Pol II

A

Eukaryotic RNA polymerase II, which transcribes protein-coding genes and most small nuclear RNAs.

22
Q

Why is the regulation of RNA polymerase II important for tissue-specific variation in specific mRNAs and proteins?

A

RNA polymerase II transcribes protein-coding genes, which are the genes that encode the proteins that make up the different cells and tissues in the body. By regulating the activity of RNA polymerase II, cells can control which genes are transcribed and how much protein is produced from each gene. This allows different tissues to express different sets of proteins, which gives them their unique characteristics.

23
Q

What is the core of RNA polymerase?

A

A complex of subunits that is responsible for DNA binding and transcription.

It is highly conserved between prokaryotes and eukaryotes.

24
Q

What is the function of the peripheral regions of RNA polymerase?

A

Responsible for interactions with other proteins. These interactions determine the specificity and efficiency of transcription.

25
Q

What are the three steps that RNA polymerase proceeds through to transcribe a gene?

A

Initiation
Elongation
Termination

26
Q

What are the steps in transcription initiation?

A
  1. RNA polymerase binding to the promoter region of a gene.
  2. DNA goes from a closed complex to an open complex
  3. We now have a so-called initial transcribing complex
27
Q

What is the difference between a closed complex and an open complex?

A

closed complex = tightly wound DNA double helix
open complex = unwound DNA double helix

28
Q

What is the role of the σ factor in transcription initiation of bacteria?

A

Converts the core RNA polymerase enzyme into a holoenzyme that is capable of recognizing and binding to promoters.

29
Q

What is the structure of the σ factor?

A

A multimeric structure (heterohexamer)

  • meaning that it is made up of multiple subunits
30
Q

How does the σ factor provide specificity for transcription initiation?

A

The σ factor interacts with specific sequences in the promoter region of a gene. This allows the RNA polymerase holoenzyme to bind to the correct promoter and start transcription at the correct site.

31
Q

What is the structure of promoters recognized by RNA polymerase (RNAP) containing σ70?

A

-35 region: TTGACA
-10 region: TATAAT
RNA start site
UP element: N17
N5-9: a variable sequence of 5-9 nucleotides

(slide 14)

32
Q

More flashcards covering slides 15-19

A

More flashcards covering slides 15-19

33
Q

What is negative regulation of gene expression?

A

A type of gene regulation in which the presence of a regulatory protein inhibits the transcription of a gene.

34
Q

What is a repressor?

A

A repressor is a regulatory protein that binds to the promoter region of a gene and inhibits its transcription.

35
Q

How does a repressor bind to the promoter region of a gene in the absence of a signal?

A

They have a higher affinity for the promoter in its unbound state.

36
Q

How does a repressor bind to the promoter region of a gene in the presence of a signal?

A

Some repressors can bind to a signal molecule, which changes their conformation and allows them to bind to the promoter region of a gene.

37
Q

What is positive regulation of gene expression?

A

Positive regulation of gene expression is a type of gene regulation in which the presence of a regulatory protein activates the transcription of a gene.

38
Q

What is an activator?

A

An activator is a regulatory protein that binds to the promoter region of a gene and activates its transcription.

39
Q

How does an activator bind to the promoter region of a gene in the absence of a signal?

A

Some activators can bind to the promoter region of a gene in the absence of a signal, but they do not activate transcription until they are bound to a signal molecule.

40
Q

How does an activator bind to the promoter region of a gene in the presence of a signal?

A

Other activators bind to the promoter region of a gene only in the presence of a signal molecule.

41
Q

Why is it important to have both negative and positive regulation of gene expression in prokaryotes?

A

Because they allow cells to respond to changes in their environment and to control the expression of genes that are essential for their survival.

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BIOL5014 - Molecular Biology (5 decks)

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