bacterial gene transfer 6.1

Question 1

what are 3 methods for bacterial gene trasnfer?

Answer 1

transformation
transduction
conjugation

Question 2

All three mechanisms require?

Answer 2

Homologous recombination

Question 3

Homologous recombination takes place when?

Answer 3

closely related DNA sequences with (extensive homology) from two distinct genetic elements are combined into a single element

Question 4

Recombination is an important ______ process

Answer 4

evolutionary

*cells have specific mechanisms for ensuring that recombination takes place and that it takes place with precision

Question 5

What is RecA protein?

Answer 5

single-stranded binding protein

• an important enzyme mediator for process of recombination
• Only competent cells are transformable

Question 6

What is competence?

Answer 6

a state in which cells are able to take up free DNA (must be able to capture and take up DNA on membrane)

Question 7

competence is related to changes in?

Answer 7

the cell surface that allow binding of DNA

Question 8

Not all bacteria can accomplish transformation, you MUST have _____ to do so

Answer 8

competence

Question 9

In the end of transformation, a single strand of transforming DNA is integrated into the chromosome using?

Answer 9

homologous recombination and then a complementary strand is synthesized

Question 10

Why is the discovery of transformation a seminal event in biology?

Answer 10

it led to experiments demonstrating that DNA is the genetic material of cells (Avery, McLeod and McCarty) and PROVED that DNA was genetic material

Question 11

What was the experiement for transformation? bacteria used? R-cell and S-cells?

Answer 11

Griffith’s experiment with pneumococcus= Streptococcus pneumoniae using S cells (smooth colony cells with capsule= virulence factor) and R cells ( rough colony cells without (incapable of making) capsule)

Question 12

DId S cells or R cells kill the rats?

Answer 12

heat killed S cells= alive
Live S cells= dead
Live R cells= alive
Live R cells + heat killed S cells= dead

Question 13

the key to Streptococcus pneumoniae being deadly is? also proved?

Answer 13

the capsule

• bc heat killed S cells with capsule didn’t kill rat BUT heat killed S + live R AND live S cells alone did kill rat
• ***DNA as genetic material

Question 14

What prevents bacterial uptake by macrophages?

Answer 14

capsular polysaccharide

Question 15

What is transduction?

Answer 15

1) transferred DNA is carried in the capsid (protein coat) of a bacteriophage.
2) The donor’s DNA replaces part or all of the viral genome in the bacteriophage core.
* Therefore the virus is now defective, bc it doesn’t have all of the genetic information for its own replication

Question 16

Transduction involves the transfer of?

Answer 16

host genes from one bacterium to a bacterial virus and then from the virus to another bacterium

Question 17

In generalized transduction random fragments of the DNA from the bacterial
chromosome are incorporated into?

Answer 17

the virus particle

Question 18

Efficiency of this type of transduction is low?

Answer 18

generalized transduction

Question 19

specialized transduction requires?

Answer 19

• -1)viral DNA to be incorporated into the host chromosome of the donor
• -2)viral DNA to then be excised from the donor host chromosome.
• -3)imprecise viral DNA excision from the host chromosome so that adjacent host genes are also excised (this virus may not be defective).
• –4)viral infection into another bacterium (recipient); transducing efficiency in this case may be very high

Question 20

What type of transduction may NOT have defective viruses after DNA is extracted?

Answer 20

specialized transduction

Question 21

Efficiency of this type of transduction is high?

Answer 21

specialized transduction

Question 22

Temperate virus

Answer 22

a virus whose genome is able to replicate along with that of its host and not cause cell death. This is called a state of lysogeny

Question 23

Provirus (Prophage)

Answer 23

the genome of a temperate virus when it is replicating within the host chromosome

Question 24

Lysogen

Answer 24

a bacterium that contains a prophage

Question 25

Lysogenic pathway

Answer 25

a series of steps after virus infection leading to replication of viral genome as a prophage

Question 26

Lytic pathway

Answer 26

series of steps after virus infection that leads to virus replication and destruction of the host cell

Question 27

Some temperate phages cause

Answer 27

phenotypic changes in the bacteria they infect even without transducing bacterial genes

Question 28

What does state of lysogeny mean?

Answer 28

a virus being able to replicate its genome (as well as its host) and NOT cause cell death

Question 29

lambda phage is a type of?

Answer 29

temperate phage

Question 30

In the case of temperate phages such as lambda phage, the virus genome gets incorporated into the?

Answer 30

bacterial DNA at the same spot each time

Question 31

temperate phage have what type of transduction?

Answer 31

specialized transduction

-only a few of the same bacterial genes are transduced each time with RARE mistakes

Question 32

In the normal lytic event the excision of phage DNA from the host DNA leads to?

Answer 32

normal phage production without host DNA excision

Question 33

In the lysogenic state, viral genes

confer new?

Answer 33

properties on the cell

Question 34

phage conversion are examples of _____ state

Answer 34

lysogenic state

Question 35

Give 2 examples of phage conversion?

Answer 35

1)toxin production by pathogenic bacteria
such as Corynebacterium diphtheriae
2) surface polysaccharide structure in
Salmonella anatum