ch 6 the genetics of bacteria and their viruses

Question 1

characteristics of bacteria

Answer 1

• single celled
• prokaryotic (no membrane-bound organelles)
• have only 1 circular chromosome

Question 2

minimal medium

Answer 2

medium containing only inorganic salts, a carbon source, and water

Question 3

prototroph

Answer 3

a microorganism capable of growing on minimal medium (wild type)

Question 4

auxotroph

Answer 4

a microorganism that will only grow on medium supplemented with a specific compound (not required by the wild type)

Question 5

selective medium

Answer 5

only certain genotypes are able to grow
eg. minimal media selects against auxotrophs

Question 6

differential medium

Answer 6

genotypes can be distinguished from each other based on how the organism grows on the medium
eg. staining of cells able to utilize lactose

Question 7

3 mechanisms of DNA exchange in bacteria

Answer 7

conjugation
transformation
transduction

Question 8

conjugation

Answer 8

the union of bacterial cells during which genetic info is transferred from donor (F+ or Hfr) to recipient (F-)
- requires cell to cell contact

Question 9

transformation

Answer 9

introduction of foreign DNA material through external application; exchange of genetic info btw bacteria and environment
- uptake of ‘naked’ DNA

Question 10

transduction

Answer 10

movement of genetic material from donor to recipient through a bacteriophage vector
- bacteriophage injection

Question 11

is transfer of info directed?

Answer 11

yes, one strain is the donor and the other is the recipient

Question 12

F (fertility) factor

Answer 12

bacterial episome (present on plasmid or chromosome) which allows a bacterial cell to be the donor during conjugation

Question 13

plasmid

Answer 13

extrachromosomal, autonomously replicating, circular DNA

Question 14

properties of the F-factor

Answer 14

1. enables the production of the pili (proteinaceous attachment tube btw cells)
2. able to replicate (cell division and conjugation)
3. prevents conjugation between F+ cells

Question 15

Hfr (high frequency of recombination)

Answer 15

a bacterial cell in which the F factor is integrated into the chromosomes; during conjugation, the F factor acts as the origin of chromosomal transfer

Question 16

exconjugate

Answer 16

a bacterium that has undergone conjugation

Question 17

endogenate

Answer 17

the endogenous recipient chromosome

Question 18

exogenate

Answer 18

the exogenous donor chromosome

Question 19

merozygote

Answer 19

a cell which is a partial diploid, containing both an endogenote and an exogenote

Question 20

interrupted mating experiment

Answer 20

1. allow two strains to conjugate
   Hfr strain and F- strain
2. samples taken at specific time intervals and conjugation is interrupted
3. plate on medium with streptomycin (inhibits HFR, only want to see growth of F- strain) and score for ton r, lac, gal, azi r

Question 21

results of interrupted mating experiment

Answer 21

genetic markers appear in the exconjugates at specific times
- there is a fixed point at which transfer begins (origin), and a linear order to the transfer of markers
- time taken to transfer is related to the distance btw the marker and the origin of transfer

Question 22

origin of transfer

Answer 22

the fixed point from which DNA transfer begins during conjugation

Question 23

the F integration site determines

Answer 23

the order of marker transfer from Hfr
- relative position of markers is constant

Question 24

three things mapping by minutes tells us

Answer 24

1. order of transfer - linear arrangement of genes
2. time of transfer - proportional distance btw genes
3. can also determine position and orientation of the origin

Question 25

gradient of transfer

Answer 25

genes nearest origin are transferred at a higher frequency than those farthest from the origin
- where you plateau is related to where you enter the cell

Question 26

what happens to linear DNA in bacteria

Answer 26

it degrades

Question 27

increasing conc of DNA results in

Answer 27

a higher frequency of transformation

Question 28

higher co-transformation frequency =

Answer 28

closer to selected marker

Question 29

bacteriophage

Answer 29

“bacteria eater”
a virus that infects bacteria
have a nucleic acid and protein coat

Question 30

lytic cycle

Answer 30

mode of infection in which the bacteriophage genome enters the bacterium, replicates, lyses the cell, and progeny are released

Question 31

virulent bacteriophage

Answer 31

a bacteriophage which always completes the lytic cycle upon infection (unable to become a prophage)

Question 32

prophage

Answer 32

a phage genome which is integrated into a bacterial chromosme

Question 33

lysogenic bacterium

Answer 33

bacterial cell capable of spontaneous lysis due to the release of a prophage from the bacterial chromosome

Question 34

lysogenic

Answer 34

the state of a bacterial cell that has a prophage integrated into its chromosome

Question 35

temperate bacteriophage

Answer 35

a phage capable of entering the lysogenic cycle with its host

Question 36

generalized transduction

Answer 36

faulty head-stuffing

Question 37

specialized transduction

Answer 37

faulty outlooping
- results in phage with chromosomal DNA
- requires lysogenic cycle