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MCB 150 > Genetic Regulation + Viruses > Flashcards

Genetic Regulation + Viruses Flashcards

1
Q

Cost of making proteins per second

A
  • 120 ATP per second
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2
Q

Constitutive expression

A
  • genes that are needed at all times, and this are expressed at all times.
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3
Q

Where can regulation occur?

A
  • at all stages of protein synthesis - transcription, translation, post-translation
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4
Q

Where regulation mostly occurs

A
  • transcription initiation
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5
Q

Why does regulation most regularly occur at transcription initiation?

A
  • because it saves the cell the most energy
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6
Q

What is there a trade off between when regulation occurs?

A
  • energy savings and speed at which the change is put into effect.
  • so altering protein activity doesn’t get that ATP back, but change is immediately noticeable
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7
Q

Operon

A

Multiple protein coding regions under the control of a single promoter - a polycistronic mRNA

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8
Q

Things coded for by the lac operon and their regions

A
  • B galactosidase - Lac Z
  • Lac Permease - LacY
  • Transacetylase - LacA
  • repressor protein that binds to the promoter region by default - LacI
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9
Q

Function of B-galactosidase

A
  • breaks down lactose into galactose and glucose
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10
Q

Function of Lac permease

A
  • allows passing of lactose from outside the cell to inside the cell.
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11
Q

Relationship of glucose levels and cAMP levels

A
  • if Glucose levels decrease, cAMP levels increase
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12
Q

Describe the process of how glucose impacts expression of the lac operon genes

A
  • CAP binds to cAMP
  • CAP-cAMP complex binds to CAP site
  • this complex interacts with the carbon terminal domain of RNA polymerase
  • this increases rate of transcription of lac genes
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13
Q

Describe what would happen if the levels of glucose in a bacterial cell went up (more glucose available than lactose)

A
  • levels of cAMP would decrease
  • thus less cAMP would bind to the CAP
  • less complex (CAP-cAMP) would bind to CAP site
  • less interaction between C terminal domain of a subunit of RNA pol
  • thus lowers rate of transcription of the lac operon genes, less of the enzymes involved in lactose metabolism would be made.
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14
Q

Ratio of protein ducts of the lac operon from B-gal, permease, transacetylase

A
  • 10:5:2
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15
Q

How can ratio of proteins be adjusted from a single mRNA

A
  • level of mRNA stability
  • level of translation initiation
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16
Q

How can level of mRNA stability be adjusted at the level of mRNA stability

A
  • lac mRNA degraded from 3’ end
  • because bacterial mRNAs have rapid turnover, it allows for a quick response to changes in environment
17
Q

How can a single mRNA be adjusted at the level of translation initiation

A
  • ‘strength’ of shine dalgarno sequence (how close is it to the consensus sequence?) affects how much protein is made from that gene
  • also affected by availability of shine dalgarno sequence - is it folded into secondary structure or blocked by proteins etc.
18
Q

How do we define the lack of operon specifically?

A
  • is inducible - is off by default, but turned on when needed.
19
Q

How can we define the trp operon by default?

A
  • repressible
  • as it is on by default, can be turned off when tryptophan is abundant.
20
Q

Tryptophan operon structure

A
  • Trp Repressor
  • followed by promoter and operator region
  • followed by Trp L (Leader) - attenuator present in TrpL
  • Trp L is followed by 5 different genes - E,D,C,B,A
21
Q

Initially, why can’t the Trp repressor bind to its operator

A
  • because it is an aporepressor - it can’t work without another molecule
22
Q

What does tryptophan act as

A
  • a co-repressor
  • when lots of tryptophan is made, it binds to the trp repressor, which allows it to then bind to the operator and prevent transcription by not allowing RNA pol to transcribe the gene
23
Q

What is another example for allosteric regulation or feedback inhibition of proteins

A
  • regulation of PFK in glycolysis
24
Q

Role of the mediator

A
  • binds in between gene specific TFs and the core promoter complex (TFs and Pol II)
25
Q

What are the facts of gene/tissue specific factors? (Activators/repressors)

A

Affect ability of GTFs to bind core promoter sequence
• Stimulate RNA polymerase II to proceed to elongation
• Recruit chromatin-remodeling complexes

26
Q

How do Upstream TFs and GTFs work

A
  1. An activator binds to an enhancer
  2. The activator enhances the ability of TFIID to bind to the TATA box
  3. TFIID promotes the assembly of the pre-initiation complex
  4. Mediator binds to Pre-initiation complex, but initiation doesn’t happen
  5. Activator bind to a distant enhancer and a coactivator complex to interact with mediator - this interaction causes RNA polymerase to proceed to the elongation stage of transcription.
27
Q

What else can activators recruit

A

ATP-dependent chromatin remodeling complexes

28
Q

Activators recruit ATP-dependent chromatin remodeling
complexes which in turn:

A

change locations/spacing of nucleosomes
• evict histones from nucleosomes
• replace standard histones with histone variants

29
Q

What even more things can activators do

A

Can recruit histone modifying enzymes
(Covalent, but reversible fashion, involving methylation, acetylation, and phosphorylation)

30
Q

Methylation leads to

A

Silencing, making genes inaccessible

31
Q

Acetylation leads to what

A
  • enhancing/increasing accessibility for transcription
32
Q

Regulation of ferretin production

A
  • when iron levels are low, IRP (iron response protein) binds to IRE (iron response element) inhibiting translation
  • when iron levels are high, IRP binds to iron, causing conformational change that releases it from the IRE, allowing translation to proceed.
33
Q

Virus characteristics (4)

A
  • intracellular parasites
  • can persist on their own under appropriate conditions (NOT SURVIVE.)
  • can only reproduce within a host cell using tools from host - eg tRNA, ATP etc has to use from host cell.
  • simple structures, nuclei acid, protein coat and enzymes
34
Q

Viruses genomes (6)

A
  • few dozen to a few hundred genes
  • either DNA/RNA
  • can be single stranded or double stranded.
  • can be linear or circular
  • single copy or multiple copies
  • segmented or non segmented
35
Q

Most common type of virus

A
  • linear double-stranded DNA virus
36
Q

3 tasks of viral replication cycles

A
  • get in, replicate genetic material, get out.

MCB 150 (8 decks)

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