Genetic Transfer Systems Flashcards

1
Q

What are the THREE mechanisms that bacteria are able to acquire genetic information from their environment or from each other?

A
  1. Conjugation
  2. Transformation
  3. Transduction
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2
Q

What is Conjugation?

A

Transfer of DNA involving direct cell-to-cell contact mediated by pili

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3
Q

What is Transformation?

A

Uptake of free exogenous DNA by a bacterium

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4
Q

What is Transduction?

A

Transfer of DNA from one bacterium to another by a bacteriophage

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5
Q

What are the THREE outcomes for recieved DNA?

A
  1. Exist autonomously in cytoplasm of recipient
  2. Integrated into recipient chromosome
  3. Replace homologous DNA of recipient
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6
Q

What is the Recipient?

A

Bacterium that RECIEVES DNA

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7
Q

What is the Donor?

A

Bacterium that DONATES DNA

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8
Q

What is Homologous DNA?

A

Regions of DNA which are very similar between donor and recipient

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9
Q

Can DNA move unidirectionally or bidirectionally between bacterium?

A

DNA always moves in one direction

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10
Q

What do a Donor and Recipient together make?

A

Mating pair

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11
Q

What factor do E. coli donor cells contain?

A

F-factor

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12
Q

What is an F-factor?

A

Genetic element (plasmid or episome) capable of conjugative transfer

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13
Q

How many genes are contained in an F-factor?

A

20 tra genes, involved in DNA transfer

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14
Q

What proteins do tra genes encode for?

A

Proteins required for the synthesis of specialised appendages (e.g. Pili)

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15
Q

What are the functions encoded by the F-plasmid?

A
  • Attach donor to recipient
  • Provide a channel through which genetic material can be passed
  • tra genes also confer surface properties on donors that prevents contact with other donors
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16
Q

What THREE forms can an F-factor exist in within a Donor?

A
  1. F+ donor
  2. Hfr bacterium
  3. F’ donor
17
Q

How does the F+ factor exist within a Donor?

A

Exists as small covalently closed circle of DNA within the cytoplasm

18
Q

How does the Hfr factor exist within the Donor?

A

F plasmid is integrated into the bacterial chromosome, mobilising the entire bacterial genome

19
Q

How does the F’ factor exist within the Donor?

A

May contain a few other genes in a circular structure that exists free in the cytoplasm

20
Q

What does the endonuclease (TraI) do in Conugation?

A

Puts a single break (or nick) in one of the two strands at the oriT, freeing one of the two DNA strands in the plasmid to begin DNA transfer to recipient

21
Q

Do Transducing Phage contain DNA, RNA, or both?

22
Q

What are the TWO different types of Transduction?

A
  1. Generalised
  2. Specialised
23
Q

How is Generalised Transduction carried out?

A

By virulent DNA-containing phage that have a lytic cycle of infection

24
Q

What is Generalised Transduction used for?

A
  • To measure the distance between two bacterial genes
  • Done by determining how frequently two genes are included in the same transducing phage
25
What does the distance between two genes included in the same transducing phage indicate?
The closer together two genes are on the chromosome, the more frequently they will be included in the same piece of transducing DNA
26
What ability of the cell will depend on whether it can undergo Transformation or not?
Whether the cell is Competent
27
How can *E. coli* become Competent?
Through CaCl2 or LiCl2 treatment, or electroporation
28
Who discovered the phenomenon of natural transformation?
Frederick Griffith
29
Who showed that natural transformation was due to DNA that was taken up by the cell?
Oswald Avery
30
What methods can produce Artificial Transformation?
* Chemical treatment * Electroporation * Protoplast formation * Firing DNA-coated metal pellicles