Chapter 5: The Genetics of Bacteria and their Viruses

Question 1

prokaryotes

Answer 1

DNA not enclosed in a nucleus

ex. bacteria

Question 2

horizontal transmission

Answer 2

a type of gene transmission without cell division

ex. DNA transfer on a plasmid, transformation, transduction

Question 3

vertical transmission

Answer 3

transfer of DNA down through bacterial generations

Question 4

plating

Answer 4

a process whereby a small amount of a liquid culture is pipetted onto a petri plate containing solid agar medium and spread evenly on the surface with a sterile spreader

Question 5

colony

Answer 5

a mass of bacteria that is visible to the naked eye

Question 6

cell clones

Answer 6

members of a colony that have a single genetic ancestor

Question 7

prototrophic

Answer 7

can grow/divide on minimal medium (substrate only contains basic needs)
ex. WT bacteria

Question 8

auxotrophic

Answer 8

cells will not grow unless medium contains one or more specific cellular building blocks
ex. mutant bacteria

Question 9

conjugation

Answer 9

the physical union of bacterial cells

Question 10

conjugating prents act….

Answer 10

unequally (donor transfers some or all of genome into recipient)

Question 11

donor ability is a hereditary state imposed by a:

Answer 11

fertility factor (F)

Question 12

plasmid

Answer 12

nonessential circular DNA that can replicate in the cytoplasm independent of the host chromosome

Question 13

how do plasmids make single-stranded versions of themselves?

Answer 13

through rolling circle replication (the single strand that is formed/transferred then acts as a template and is converted into a double helix)

Question 14

Hfr

Answer 14

high frequency of recombination, where donor genes become incorporated in recipient’s chromosomes through cross-over’s to create a recombinant cell

Question 15

if there is no recombination or integration of transferred DNA, then…

Answer 15

transferred fragments of DNA are lost

Question 16

interrupted mating

Answer 16

put in blender to separate mating pairs at varying time intervals

Question 17

exconjugants

Answer 17

cells that had taken part in conjugation

Question 18

origin (O)

Answer 18

fixed point on donor chromosome where single-stranded DNA transfer beings

Question 19

the farther a gene is from O…

Answer 19

the later it is transferred to recipient cell

Question 20

Hfr is generated by:

Answer 20

insertion of F (donor DNA with F factor) into the ring in the appropriate place/orientation

Question 21

insertion sequences

Answer 21

regions of homology/segments of transposable elements where F (donor DNA with F factor) can be integrated, pairing region is then appropriate for cross-overs

Question 22

one end of integrated F factor DNA is the:

Answer 22

origin, where transfer of the chromosome begins. The other end is the terminus

Question 23

fertility factor exists in two states:

Answer 23

plasmid state (free cytoplasmic element that is easily transferred)
integrated state (part of circular chromosome, only transmitted very late in conjugation)

Question 24

what does broad-scale chromosome mapping use?

Answer 24

time of entry

Question 25

what does fine-scale chromosome mapping use?

Answer 25

recombinant frequency

Question 26

recombination takes place between:

Answer 26

one complete genome (endogenote-recipient) and an incomplete genome (exogenote-donor)

Question 27

merozygote

Answer 27

partial diploid during recombination stage

Question 28

what is the main rule for bacterial recombinations?

Answer 28

even number of recombinant events to keep circle intact

Question 29

F’ plasmid

Answer 29

an F plasmid carrying part bacterial genomic DNA and part F factor

Question 30

R plasmid

Answer 30

vectors that carry multiple resistances, transferred rapidly on cell conjugation

Question 31

transposon

Answer 31

the unit within which alleles for antibiotic resistance is contained

Question 32

transformation

Answer 32

uptake of fragments of DNA from the external medium, permanently changes the genotype of the recipient

Question 33

how can transformation help determine gene linkage?

Answer 33

If double transformations occur in a higher proportion than single transformations.

breakage occurs when DNA is extracted for transformation, if two genes are closer on the same chromosome, will be more likely to be carried together to be taken up, causing a DOUBLE TRANSFORMATION

Question 34

if genes are far apart and carried on separate transforming segments…

Answer 34

an independent double transformation is less likely

Question 35

lysis

Answer 35

the breaking open process

Question 36

lysate

Answer 36

the population of phage progeny

Question 37

plaque

Answer 37

a visible clear area within a bacteria plate (caused by exponential increase of lysis following cycles of infection)

Question 38

what are two forms of genetic analyses of phages?

Answer 38

plaque morphology (depends on phage genotype)
host range (phage genotype can dictate which bacterial strains able to infect)

Question 39

mixed infection/double infection

Answer 39

when one strain is infected with both parental phage genotypes (i.e. how one crosses phages)

Question 40

recombinants from phage crosses are a result of:

Answer 40

a population of events rather than a defined, single-step exchange

Question 41

selective system

Answer 41

only the desired rare event can produce a visible outcome (can be used to map mutant sites within genes-RARE)

Question 42

screen

Answer 42

a system in which large numbers of individuals are visibly scanned to seek the rare event