11.Horizontal genetic transfer in bacteria

Question 1

What are characteristic of horizontal genetic transfer

Answer 1

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

Question 2

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

Answer 2

Merozygotes (partial diploidy)

Question 3

Can plasmids transfer and replicate autonomously

Answer 3

Yes

Question 4

Can genetic transfer occur between different species

Answer 4

Yes

Question 5

What types of bacterial horizontal genetic transfer do we have

Answer 5

Transformation
Conjugation
Transduction

Question 6

What is transformation

Answer 6

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

Question 7

When does transformation occur

Answer 7

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

Question 8

What’s competent bacterial cell

Answer 8

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

Question 9

When is competence acquired

Answer 9

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

Question 10

Where is transformation used in research

Answer 10

In artificial introduction of plasmids into bacterial cell

Question 11

What kinds of artificial transformations do we have

Answer 11

-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

Question 12

Where do clones of DNA of interest in transformation grow

Answer 12

On selective medium

Question 13

What is conjugatioon

Answer 13

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

Question 14

What is exchanged in conjugation

Answer 14

Conjugation factors

Question 15

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

Answer 15

Conjugative plasmids or transposones

Question 16

What other factors can conjugative plasmids carry except conjugation factors

Answer 16

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

Question 17

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

Answer 17

Yes

Question 18

What are steps of conjugation

Answer 18

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

Question 19

What is F factor in conjugation

Answer 19

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

Question 20

In what forms can F factor exist

Answer 20

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

Question 21

What’s transduction

Answer 21

Transfer of genetic material mediated by viruses

Question 22

What kind of transduction do we have

Answer 22

Generalized and Specialized

Question 23

What’s generalized transduction

Answer 23

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

Question 24

What’s specialized transduction

Answer 24

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

Question 25

What type of nucleic acid do virion contain

Answer 25

Only one, DNA or RNA

Question 26

What's some important characteristic of viruses

Answer 26

-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

Question 27

What are some basic T4v phage components

Answer 27

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

Question 28

How do viruses infect bacteria

Answer 28

By attachment and inoculation into the cytoplasm

Question 29

What happens to host functions because of the virus

Answer 29

They are blocked

Question 30

What kind of cycle do we have in phages

Answer 30

Lytic and lysogenic

Question 31

Can phages carry toxic genes

Answer 31

Yes

Question 32

What's lytic cycle

Answer 32

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

Question 33

What's lysogenic cycle

Answer 33

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

Question 34

What does transducing phages have

Answer 34

Their particles contain host genes from donor cell

Question 35

What can phages made by specialized transduction do

Answer 35

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

Question 36

What are some results when transferring bacteria genetic material

Answer 36

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

Question 37

What is recombination

Answer 37

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

Question 38

What kind of recombination is there

Answer 38

Homologous and site-specific

Question 39

When does homologous recombination happen

Answer 39

HR occurs when there are long regions of similar nucleotide sequence

Question 40

What the process of homologous recombination

Answer 40

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

Question 41

Can different recombination sites be generated

Answer 41

Yes, depending on the break

Question 42

Where can homologous recombination occur

Answer 42

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

Question 43

Are homologous sequences short in the molecule that recombine

Answer 43

Yes

Question 44

Where does site- specific recombination occurs

Answer 44

At specific target sites with specific DNA sequence

Question 45

What are specific sites for site-specific recombination recognized by

Answer 45

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

Question 46

What happens to mechanisms in site-specific recombination

Answer 46

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

Question 47

What is SSB in homologous recombination

Answer 47

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