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LF104: Molecules, Cells And Organisms > Lecture 40. Transformation and Transduction > Flashcards

Lecture 40. Transformation and Transduction Flashcards

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Organic Chemistry 101 flashcards
1
Q

What are Streptococcus pneunomiae R cells?

A

Rough colonies, non-pathogenic

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2
Q

What are Streptococcus pneunomiae S cells?

A

Smooth colonies, pathogenic, secrete a gelatinous polysaccharide capsule

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3
Q

What happened to the mouse infected with R cells?

A

Mouse is fine - R cells are non-pathogenic

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4
Q

What happened to the mouse infected with S cells?

A

Mouse dies - S cells are pathogenic

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5
Q

What happened to the mouse infected with heat killed S cells?

A

Mouse is fine - Dead S cells are non-pathogenic

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6
Q

What happened to the mouse infected with heat killed S cells and R cells?

A

Mouse dies

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7
Q

What principle did Griffith demonstrate?

A

The transforming principle

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8
Q

What is “competence”?

A

The ability of a bacterial cell to take up extracellular (‘naked’) DNA from the environment

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9
Q

Why is recombination essential in prokaryotes?

A

Recombination results in more “fit” organisms. Leads to spread of drug resistance, novel virulence characteristics, novel metabolic capabilities etc.

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10
Q

What does transformation require?

A

Competent cells

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11
Q

When does competence occur in a bacteria’s life span and why?

A

Just before entry to the stationary phase as cells rely on quorum sensing to do something as the cells are now at risk of dying

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12
Q

What is quorum sensing?

A

The ability to regulate genes based on population density

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13
Q

What pheromone do B. subtilis cells secrete?

A

ComX

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14
Q

What happens when ComX binds to ComP?

A

The binding of ComX and ComP set off a reaction of events leading to changes in gene expression which makes cells more competent

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15
Q

What DNA can B. subtilis take up?

A

DNA of any origin

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16
Q

Can all bacteria take up DNA from any origin?

A

No - Neisseria gonorrhoeae and Haemophilus influenzae will only take up from same species

17
Q

How can the bacteria distinguish between DNA from another bacteria of the same species and from a different species?

A

It recognises specific DNA sequences

18
Q

Uptake of DNA mechanism

A
  1. DNA bind to surface protein on cell
  2. Depending on species, single or double DNA enters the cell
  3. Bind to competence-specific protein
  4. RecA mediated integration
19
Q

Can new traits be acquired through DNA uptake?

A

Yes - Gene fragment usually big enough to contain several genes

20
Q

What is transduction?

A

Transduction is genetic exchange in bacteria mediated by bacteriophages
Transfer of DNA using a phage as a vector

21
Q

What are possibly the most abundant “organisms” on earth?

A

Phages

22
Q

Where do phages live?

A

Co-exist with hosts in all environments

23
Q

What do phages influence?

A

Characteristics of host
Population dynamics
Long term evolution

24
Q

Lytic Cycle

A
  1. Attachment of phage
  2. DNA inserted into cell, circularises, replication, transcription and translation, new virions assembled
  3. Lysis and release of new virions
  4. Cycle then repeats
25
Q

What are restriction enzymes?

A

Restriction enzymes provide a defence mechanism against invading viruses. Enzymatic cleavage of the phage DNA and host DNA modified by methylation

26
Q

What is a lysogen?

A

A strain of bacteria carrying a lysogenic phage e.g. E. coli (λ)

27
Q

What is a prophage?

A

Phage in a lysogenic state

28
Q

Lysogenic cycle

A
  1. Attachment
  2. DNA inserted into cell and integrated into genome and stays there
  3. Transmitted to daughter cells
29
Q

How is the lytic cycle suppressed?

A

Expression of phage protein that stops lysis - This protein also suppresses lysis by other phage of the same type infecting the cell

30
Q

Can all phages transduce?

A

Some phages can transduce (others not)

31
Q

Can all bacteria transduce?

A

Only some bacteria are transducable

32
Q

What is generalised transduction?

A

Transfer of any DNA to the recipient cell by lytic or lysogenic phage

33
Q

What is specialised transduction?

A

Transfer of specific genes via lysogeic phages

LF104: Molecules, Cells And Organisms (33 decks)

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