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Microbiology > 11.Horizontal genetic transfer in bacteria > Flashcards

11.Horizontal genetic transfer in bacteria Flashcards

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Biology 101 flashcards
1
Q

What are characteristic of horizontal genetic transfer

A

-It’s only in one direction-from donor to the recipient
-only part of a chromosome is transferred in case of foreign DNS

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2
Q

what’s exception to the rule that only a part of the chromosome is transferred in case of foreign DNA

A

Merozygotes (partial diploidy)

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3
Q

Can plasmids transfer and replicate autonomously

A

Yes

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4
Q

Can genetic transfer occur between different species

A

Yes

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5
Q

What types of bacterial horizontal genetic transfer do we have

A

Transformation
Conjugation
Transduction

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6
Q

What is transformation

A

Introduction of foreign DNA from the extracellular environment into the bacterial cell which is maintained in a heritable form

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7
Q

When does transformation occur

A

In a certain stage of growth and it’s finely regulated

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8
Q

What’s competent bacterial cell

A

Bacterial cell that’s able to uptake DNA from the extracellular environment

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9
Q

When is competence acquired

A

In a particular stage of the growth curve and under particular nutritional conditions

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10
Q

Where is transformation used in research

A

In artificial introduction of plasmids into bacterial cell

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11
Q

What kinds of artificial transformations do we have

A

-Chemical: By CaCl2(Escherichia coli and other Gram -); It’s partial permeabilization in ice and then heat shocked. As the result, dsDNA enters the cell
-Physical: it can be used in all cells; uses process called electroporation which enhances permeability using electric field. Electric shock generates transient spores into the membrane. As the result, dsDNA enters the cell

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12
Q

Where do clones of DNA of interest in transformation grow

A

On selective medium

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13
Q

What is conjugatioon

A

transfer of genetic material that requires physical contact between the donor and recipients cell. Transfer of plasmids or chromosome portions

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14
Q

What is exchanged in conjugation

A

Conjugation factors

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15
Q

What is system that allows physical exchange, in +conjugation*, encoded by

A

Conjugative plasmids or transposones

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16
Q

What other factors can conjugative plasmids carry except conjugation factors

A

Genes for antibiotic resistance, toxins, colicines, complete metabolic pathway, etc.

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17
Q

Cam conjugation occur between 2 species of different genera(genus)

A

Yes

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18
Q

What are steps of conjugation

A

F+ donor containing F plasmid is capable of synthesizing sex pili
1.Contact: Sex pilus contacts the recipient F- cell
2. Activation of DNA transfer: plasmid is activated for transfer when endonuclease cleaves one strand of DNA at origin of transfer
3. Plasmid transfer: Sex pilus retracts and pulls donor and recipient cells together. F plasmid is transferred as single stranded DNA molecules
4. Synthesis of functional plasmid: Complementary strands to both F plasmid strands are synthesized in the donor and recipient cells. Both cells are F+ and synthesize sex pilus

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19
Q

What is F factor in conjugation

A

Conjugative plasmid that is able to integrate into the host chromosome or to exist in episomal form. It encodes for all the genes necessary for the conjugation process

20
Q

In what forms can F factor exist

A

3:
-Free plasmid(episomal form)-independently from the host genome
-Plasmid integrated in the host genome
-F’ plasmid, with part of the host chromosome integrated into the plasmid

21
Q

What’s transduction

A

Transfer of genetic material mediated by viruses

22
Q

What kind of transduction do we have

A

Generalized and Specialized

23
Q

What’s generalized transduction

A

Foreign DNA fragments are transferred as parts of the phage genome.

24
Q

What’s specialized transduction

A

Temperate phages are vectors of foreign DNA fragments. A portion of host genome is improperly integrated into the phage DNA because the viral DNA was integrated in the host chromosome

25
Q

What type of nucleic acid do virion contain

A

Only one, DNA or RNA

26
Q

What’s some important characteristic of viruses

A

-Do not increase in size or replicate by binary fission
-Viral genome does not encode machinery for the production of energy or metabolism
-Viral genome does not encode machinery for translation

27
Q

What are some basic T4v phage components

A

Head(which contains DNA),
Neck and collar,
Core,
Sheath,
End plate,
Fibers

28
Q

How do viruses infect bacteria

A

By attachment and inoculation into the cytoplasm

29
Q

What happens to host functions because of the virus

A

They are blocked

30
Q

What kind of cycle do we have in phages

A

Lytic and lysogenic

31
Q

Can phages carry toxic genes

A

Yes

32
Q

What’s lytic cycle

A

Virulent phages. Often called reproductive cycle. Virus enters the cell and virus is repeatedly replicated until the cell lyses, releasing phages

33
Q

What’s lysogenic cycle

A

Temperate phages. It doesn’t kill bacteria. It creates many copies of viral DNA

34
Q

What does transducing phages have

A

Their particles contain host genes from donor cell

35
Q

What can phages made by specialized transduction do

A

They are defective and can transduce the genes for galactose catabolism or the production of a toxin

36
Q

What are some results when transferring bacteria genetic material

A
  1. Degradation by recipient’s enzymes (usually)
  2. Autonomous replication(only if it possesses origin of replication)
  3. Recombination with recipient chromosome and integration
  4. CRISPR/Cas degradation of donor DNA as an antiviral response mechanism
37
Q

What is recombination

A

Physical exchange of DNA between two genetic elements that involves breaks and re-ligation of DNA during the rearrangement

38
Q

What kind of recombination is there

A

Homologous and site-specific

39
Q

When does homologous recombination happen

A

HR occurs when there are long regions of similar nucleotide sequence

40
Q

What the process of homologous recombination

A
  1. dsDNA of the donor is nicked by endonuclease
  2. ssDNA binding protein binds to the DNA where one of the ends of a strand is bounds by different proteins among which SSB and RecA
  3. RecA induces the annealing betwen homologous DNA with complementary region on the recipient DNA(strand invasion)
  4. At the end, two DNA molecules are separated by by the resolvase, which cleaves and separates the DNA at the recombinant sites
41
Q

Can different recombination sites be generated

A

Yes, depending on the break

42
Q

Where can homologous recombination occur

A
  1. Between plasmids: Recombination between two plasmids leads to a chimeric form
  2. Between plasmid and recipient chromosome: when plasmid recombinates with a chromosome, integration occurs
43
Q

Are homologous sequences short in the molecule that recombine

A

Yes

44
Q

Where does site- specific recombination occurs

A

At specific target sites with specific DNA sequence

45
Q

What are specific sites for site-specific recombination recognized by

A

Specific enzymes that are able to recognize and bind the site for site-specific recombination

46
Q

What happens to mechanisms in site-specific recombination

A

-Viral genomes are inserted into the host chromosome
-specific genes are inserted during transposition

47
Q

What is SSB in homologous recombination

A

Protein that keeps two parts of a nicked strand separated because they tend to connect

Microbiology (20 decks)

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