Genes: Organisation and Function > Lecture 7 > Flashcards

Lecture 7 Flashcards

(26 cards)

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1
Q

Tryptophan operon regulation in Bacillus subtilis:

3

A
  • Alternate, mutually exclusive stem-and-loop structures in the mRNA lead to termination or anti-termination
  • High tryptophan leads to TRAP forming (C&D) resulting in anti-termination
  • antiTRAP protein binds to inactivate TRAP, regulated by uncharged tRNAtrp
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2
Q

Regulation of gene expression is mediated by

4

A
  • Positive/negative
  • DNA-binding/RNA binding
  • Regulating transcription initiation/termination
  • Most are regulated by an effector molecule having an allosteric effect on the conformation and activity of the protein
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3
Q

Riboswitches influence gene expression in eukaryotes (some in fungi and plants) by..
(4)

A
  • Altering the structure in the mRNA through the binding of an effector molecule, influencing gene expression by..
  • Transcription termination (attenuation)
  • Translation initiation
  • No regulatory protein involved
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4
Q

Alternative structures of riboswitches

2

A
  • The normal confirmation does not result in transcription termination, but upon binding by an effector molecule
  • A change in confirmation results in transcription termination
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5
Q

Riboswitch example:

2

A
  • SAM is a small effector molecule that binds when there is enough in the cell.
  • When not bound 2&3 bind, but when bound 1&2 pair and 3&4 pair and termination follows
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6
Q

Other riboswitches examples:

6

A
  • Coenzyme B12
  • Guanine
  • Lysine
  • Adenine
  • Thyamine
  • Flavin
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7
Q

Bacteriophage lambda:

2

A
  • A simple model organism
  • Temperate bacteriophage of E.coli
  • Lysis or lysogeny are the binary outcomes based on regulatory events of genes
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8
Q

The Lambda life cycle:

A
  • Infection of a cell
  • 50kb linear genome circularises via cohesive sticky ends within the cell
  • Either lytic growth (phage infects cell and replicates new phage, cell burst etc)
  • OR lysogenic growth ohage
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9
Q

The Lambda lytic pathway:

A
  • Phage infects cell
  • 50kb genome circularises using sticky ends
  • DNA replicates using host machinery
  • Cells lyses and lambda infects new cells
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10
Q

The lambda lysogenic pathway

A
  • Phage infects cell
  • 50kb genome circularises using sticky ends
  • DNA integrates into the cell chromosomes and lambda repressor is expressed
  • Replicates with cell machinery until the repressor is turned off
  • lysis follows
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11
Q

Induction

A
  • The lysogen is induced into the lytic cycle

- Often occurs under host cell stress

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12
Q

Lambda genome parts:

7

A
  • Cos sticky ends circularise
  • Head protein genes
  • Tail protein genes
  • Lysis genes for breaking open the cell
  • Integration and excision of E.coli
  • DNA replication genes
  • Regulatory functions
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13
Q

Phage lytic development involves:

A
  • A cascade of gene expression from early to middle to late genes
  • New phage RNAP, sigma factors, promoters and anti-termination factors are used to progress to the next stage of gene expression
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14
Q

Early genes:

A
  • Phage genes are transcribed by host RNA polymerase
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15
Q

Middle genes:

A
  • Early product causes transcription of middle genes
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16
Q

Late genes:

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A
  • Middle product allows transcription of late genes containing phage components
17
Q

Early genes are divided into two groups: Immediate early genes encode:

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A
  • Are transcribed by host RNAP from PL and PR
  • cro from PL = negative regulator
  • N from PR= antiterminator, which allows transcripts to extend into delayed early genes
18
Q

Early genes are divided into two groups: delayed early genes encode:

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A
  • Transcription initiates at PR and pQ
  • cII/cIII = regulators, using 7 recombination genes and 2 replication genes
  • Q = anti-terminator, allow transcripts to extend into late genes
19
Q

Late genes:

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A
  • 10 head genes
  • 11 tail genes
  • 2 lysis genes
20
Q

cIII

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A
  • maintains cII

- used in lysogeny

21
Q

N

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A
  • anti-terminator
  • Turns on delayed early genes
  • used in lysogeny and lysis
22
Q

cI

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A
  • lysogenic repressor

- lysogeny

23
Q

cro

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A
  • negative regulator
  • turns off repressor
  • lysis
24
Q

cII

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A
  • turns on repressor

- lysogeny

25
Q
- anti-terminator - turns on late genes - used in lysis
26
The promoters for the lytic cycle are
- PL - Pr - PR'
Genes: Organisation and Function
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