Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

MIMM 323 > 9.2 - Gene Transfer > Flashcards

9.2 - Gene Transfer Flashcards

1
Q

What are the three major ways genes get transfered among bacteria?

A

o Transformation
o Conjugation
o Transduction

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

What are the two types of transformation?

A

Aritficial

Natural

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

What happens in artificial transformation?

A

We push the cells to be competent and be able to integrate the DNA of interest. Getting E. coli to be competent involves the use of reagents such as CaCl2, mercaptoethanol, the use of heat shock or electroporation, etc.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

What is natural transformation mediated by?

A

Specific gene encoding uptake systems

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

What are examples of natural transformation in gram positive non specific DNA, QS regulation?

A

(1) Streptococcus

(2) Bacillus

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

What are examples of natural transformation in gram negative using specific DNA-tag which uses Pilli type IV?

A

(1) Neisseria.
(2) Haemophilus.
(3) Vibrio cholerae (use different system using Type 4 pili that extends and retracts. This system builds from inner membrane and expands to outer membrane

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

What does the pilus bind to in vibrio cholerae and what happens to it?

A

dsDNA. It then retracts by depolymerizing the pilus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

What happens after depolymerization of pilus?

A

ComEA binds to dsDNA and pulls it through the polus.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

What happens when dsDNA unwinds?

A

One strand enters the cytoplasm through ComEC channel; the other strand is degraded

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

What does RecA recuit?

A

ssDNA to homologous site for integration

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

How does conugation start?

A

The F+ plasmid donor extends the sex pilus component of its T4SS, making contact with the F- recipient cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

What happens after contraction of the pilus?

A

Contraction of the pilus draws the two cells together. Relxase unwinds DNA at oriT; a second relaxase is recruited to this bubble

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

What happens at the nic site of OriT?

A

One strand of the F factor is nicked. One relaxase attaches to the 5’ end of the nicked strand and transfers it through the T4SS. The other relaxase remains in the donor and unwinds the DNA

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

What happens to the strand remaining in the donor?

A

It replicates by DNA Pol III

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

What happens once the transferred strand is in the recipient?

A

It circularizes and replicates by DNA pol III. The recipient has ben converted to a donor

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

How do you create and Hfr strain to mobilize a chromosome?

A

Copies of insertion sequence IS3 recombine to integrate F plasmid into the chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

How does transfer of chromsomal genes on an Hfr strain start?

A

F pilus from Hfr donor contacts the F- recipient cell

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

What happens once the F- recipient cell is contacted?

A

T4SS transfers one strain of donor chromsome. Second strand is synthesized in the recipient cell.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

What happens after the second strand is synthesized in the recipient cell?

A

The connections between the cells is lost. Hfr donor resynthesizes transferred strand of the chromsome.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

What happens after the Hfr donor resynthesizes?

A

A douvle crossover event via homologous recombination exchanges alleles between donor DNA and recipient chromosome

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

What happens after recombination?

A

Linear DNA is lost; recipient chromsome is now prototrophic for all four genes.

22
Q

What are the type of plasmids that can participate in conjugation events?

A

(1) The F plasmid of E. coli.
(2 The RK2 plasmid in other gram-negatives.This plasmid is known because it can travel between very different bacteria.
(3) The pTi (plasmid tumor inducing): it can transform recipient cell into tumor cells

23
Q

What are some characteristics of plasmids?

A

(1) They have their own origin of replication called OriV (V stands for vegetative).
(2) Plasmids also have an OriT sequence. This is the Origin of transfer. It is the sequence from which the plasmid starts transferring.

24
Q

What is OriT recognized by?

A

OriT is recognized by specific proteins that will bring the plasmid to the conjugation pore complex.

25
Q

How does the crown gall phenotype occur?

A

Crown gall phenotype in trees is due to a bacterial plasmid (pTi) transferred to plant cells. This is an example of “trans-Kingdom sex”.

26
Q

How is the pTi plasmid transferred?

A

Using type IV secretory system

27
Q

What is agrobacteria?

A

The bacteria that transfer the pTi plasmid

28
Q

What happens when plants get cut?

A

They will secrete specific substances that the other agrobacteria will recognize. So agrobacteria will move by chemotaxis to the site of the wound. Agrobacteria need to gather at a certain density at the site of the wound. They will not induce conjugation until a certain density of bacteria is reached.

29
Q

What do agrobacteria use and why?

A

QS mediated by a molecule called Acyl Homoserine Lactone to know when it is time to mobilize the pTi and form the conjugation apparatus (type VI).

30
Q

What happens when pTi gets inside the plant cell?

A

They will inject themselves in the plant genome. Then it will get expressed and transform plant tissues into tumors called crown gall.

31
Q

What are opines?

A

Low molecular weight compounds whose synthesis is catalyzed by specific genes on the pTi plasmid.

32
Q

Why is it advantageous for crown gall to produce opines?

A

(1) Opines are a source of food for agrobacteria, and agrobacteria only.
(2) Other species don’t have the metabolic pathways to process opines.
(3) Opines are therefore very selective

33
Q

What are the applications in the agro-tech industry?

A

Bacillus thuringiensis makes spores that contain a toxin called crystalline toxin that is a powerful insecticide. Agro-tech companies have isolated that gene, integrated it in agrobacteria genome so that the gene can be transferred to plants and the plant starts producing the insecticide.

34
Q

What is conjugation transfer also referred to as?

A

Type IV secretory system

35
Q

What is transduction?

A

The process by which foreign DNA is introduced into a cell by a phage. In some cases, when the phage particle is being assembled inside a bacterium during infection, some bacterial genes get incorporated into the phage capsid.

36
Q

What happens when phage infects new bacterial cells in transduction?

A

When that phage infects new bacterial cells, those genes will get transferred to the new host. They can be integrated to that host genome via homologous recombination and end up being expressed.

37
Q

What is special about transduction?

A

It does not require physical contact between the donating and recipient cell.

38
Q

What is rhodobacter capsulatus?

A

A type of photosynthetic bacteria that make their own phage

39
Q

How do rhodobacter capsulatus make their own phage?

A

Some of the cells will lyse and release particles that look like phage and contain pieces of the chromosomes. i.e. some of the Rhodobacter capsulatus will commit suicide and donate parts of their DNA. These pieces of DNA can be picked by other Rhodobacter capsulatus.

40
Q

What is rhodobacter capsulatus an example of?

A

Natural phase transduction DNA exchange mechanism.

41
Q

What are some controversial gene transfer methods?

A
  • Bacteria make tubules to transfer rna and proteins

- There are vesicles which are secreted

42
Q

What are the 3 barriers for genetic exchange?

A

(1) Limits of homologous recombination
(2) Restriction endonuclease systems
(3) CRISPR cassettes

43
Q

What does phage transduction rely on?

A

homologous recombination

44
Q

What is needed in order for homologous recombination to occur?

A

The DNA doesn’t need to be exactly the same, but somewhat similar. Once the DNA becomes too divergent, then homologous recombination cannot occur, and therefore transduction cannot occur.

45
Q

What do endonucleases do?

A

Each endonuclease recognizes a specific DNA sequence and cuts it.

46
Q

Why don’t bacteria cut their own DNA with their restriction endonuclease systems?

A

Because of the action of methyl transferases. Every restriction endonuclease has a corresponding methyl transferase which recognizes the same sequence as the endonuclease and will methylate it. This methylation prevents the cutting of the host DNA.

47
Q

What happens when exogenous DNA enters the cell?

A

It is not methylated and will therefore get cut. This will destroy the gene which will encounter genetic exchange. Once a cell acquires a restriction endonuclease system, it will be stuck with that system.

48
Q

How many types of restriction endonucleases are there?

A

3

49
Q

What are endonucleases an example of?

A

Toxin-antitoxin system

50
Q

What is Crispr?

A

If a bacterium is able to survive a phage infection, it becomes immune to that phage. So CRISPR is a kind of acquired immunity

51
Q

What happens when bacteria takes a piece of phage DNA

A

It will insert the DNA in a locus called CRISPR locus. When that phage infects again, the sequence of CRISPR corresponding to parts of the phage DNA will get transcribed.The corresponding RNA will bind to an endonuclease and acts as a probe that will direct the endonuclease towards the infecting phage DNA. The endonuclease recognizes a specific sequence of the phage DNA (thanks to the RNA) and will cut that DNA, thereby preventing the establishment of an infection. CRISPR doesn’t turn on the host genome.

MIMM 323 (26 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions