Chapter 9: Genetics of Bacteria and Their Viruses

Question 1

What is mobile DNA?

Answer 1

sequences that can be transferred between DNA molecules from one cell to another. This is a unique feature of bacterial genetic systems.

Question 2

Do bacterial cells undergo meiosis?

Answer 2

no, they have haploid and diploid lifecycle stages

Question 3

Define prototrophic

Answer 3

capable of synthesizing all of the necessary biochemical nutrients from simple inorganic nutrients.

Question 4

can a prototrophic bacteria grow on MM?

Answer 4

yes, it can make everything it needs

Question 5

Define auxotrophic

Answer 5

a bacteria that requires one of more specific nutrients in order to survive. genetic defect is blocking the nutrient producing pathway

Question 6

can an auxotrophic bacteria grow on MM?

Answer 6

no, it needs more nutrients. it can grow on MM if it is supplied with the stuff it cannot synthesize.

Question 7

What is a carbon source mutant?

Answer 7

a mutant bacteria that cannot use a specific type of carbon source as energy. Ex, being able to grow in the presence of glucose, but not being able to grow in the presence of lactose (Lac-)

Question 8

Transformation

Answer 8

process of bacterial cells taking up DNA from their environment. begins with recipient cells uptake of a DNA fragment from the surrounding medium, and terminates with ONE strand of donor DNA replacing the homologous segment in the recipient DNA.

Question 9

the ability for a cell to undergo transformation relies on the ____ of the cell.

Answer 9

competency

Question 10

If 2 markers can be transformed together, what does this indicate about their location?

Answer 10

they are very close together and can be taken up by the recipient DNA at the same time.

Question 11

What is cotransformation?

Answer 11

when 2 genes simultaneously transform and enter the recipient cell. indicates that the 2 genes are close together if the occurrence of the 2 gene transformation is greater than the product of 2 single gene transformation occurrences.

Question 12

The F+ factor is located in the ____ cell

Answer 12

donor cell

Question 13

if the fertility factor is integrated into the main bacterial chromosome of the recipient cell becomes an _____ cell

Answer 13

Hfr cell. high frequency of recombination.

Question 14

What is an episome?

Answer 14

a genetic element that can exist free in the cell or as a segment of DNA integrated into the chromosome

Question 15

If an F+ strain and an F- strain is mixed:

Answer 15

all cells become F+

Question 16

If an Hfr strain and an F- strain is mixed,

Answer 16

Hfr cells go unchanged, and some F- cells will remain F-

Question 17

What is conjugation?

Answer 17

the mating between an F- cell and an Hfr/F+ cell.

Question 18

Does the pileus extend from the Hfr cell or the F- cell?

Answer 18

the Hfr/F+ cell/ the cell containing the fertility factor.

Question 19

contact by the pileus forms the _____ bridge, here genetic transfer of DNA occurs

Answer 19

conjugation bridge

Question 20

How does DNA replicate in a bacterial cell undergoing conjugation?

Answer 20

ROLLING CIRCLE REPLICATION.

Question 21

Why is it possible that an F- cell that underwent conjugation will still remain F-?

Answer 21

DNA transfer begins within the fertility factors and drags some of the DONOR main bacterial chromosome genes with it. the F- cell might stay F- because not all of the F+ factor was transferred.

Question 22

How does conjugation aid in recombination?

Answer 22

Genetic variation/crossing overof the donor cell is not possible because when the fertility factor was transferred from the donor to the f- cell, part of the donor’s main bacterial chromosome was pulled along with it, and the transferred genes can thus undergo recombination with the recipient cell genes.

Question 23

The Hfr strand transferes a _____ strand of DNA through the conjugation tube to the recipient cell

Answer 23

single strand.

Question 24

Outline the process of Hfr transfer.

Answer 24

1) Hfr cells contains bacterial chromosome with F+ factor, and the other cell is just an F- cell.
2) Hfr cell begins rolling circle replication
3) Hfr cell transfers a single strand of DNA, beginning of replication of transferred strand
4) conjugation tube breaks apart, and the original Hfr still has its original amount of DNA even though it transferred part of it, due to rolling circle replication.the F- cell copies the single strand it was given
5) recombination takes place between the Hfr donor fragment and the F- main bacterial chromosome.
6) if F is not transferred, or not integrated into the recipient main bacterial chromosome, the recipient remains F-

Question 25

What is interrupted mating?

Answer 25

allows gene mating by deliberately interrupting DNA transfer during conjugation at different times.

Question 26

What is the standard interruption mating pairs?

Answer 26

a prototrophic, antibiotic sensitive Hfr strain and an auxotrophic, antibiotic resistant F- strain.

Question 27

How does the medium allow for interruption mating to determine gene mapping?

Answer 27

the medium that the conjugation pairs are plated on prevents the growth of the Hfr parents and only supports the growth of specific recombinants that can grow on streptomycin AND grow their own nutrients.

Question 28

what is "time of entry"

Answer 28

time where no recombinants were detected.

Question 29

T/F The number of recombinants in each curve of an interruption mating graph will increase with length of time of mating

Answer 29

true, they will eventually plateau though.

Question 30

What is an F' factor?

Answer 30

an unusual strain that is produced by an incorrect F factor EXCISION. also called partial diploids because they are caused by a breakage and a reunion that takes place between non-homologous sequences at the boundary of F and nearby chromosomal DNA. This causes PART OF THE RECIPIENT GENOME TO BE DIPLOID, but not all of it.

Question 31

What is transduction?

Answer 31

transfer of bacterial genes between bacterial cells mediated by viruses.

Question 32

T/F: bacteriophages are obligate parasites

Answer 32

true

Question 33

Describe the Lytic life cycle of a bacteriophage

Answer 33

phage injects DNA into host, where the phage DNA uses the host machinery to replicate itself and form proteins. the phage proteins assemble together to make a mature phage, and when the cell breaks apart from stress, it will LYSE and release a bunch of mature prophages.q

Question 34

How would you tell if a phage infection was present on your plates of bacteria?

Answer 34

would manifest as Plaques; clear areas on the plate where no bacteria is.

Question 35

What is a host range

Answer 35

the phage's ability to infect and use a variety of different bacterial hosts.

Question 36

How can you characterize phage genomes?

Answer 36

using plaque size characterization and host ranges

Question 37

What is bacteriophage mixed infection?

Answer 37

when a susceptible bacterial cell is infected with two different viruses at the same time to test for recombination

Question 38

H+, H-, r+ r- genotypes of phages?

Answer 38

``` H+= can only infect strain 1 of bacteria H-= can infect both strains of bacteria r+= slow lyses and small plaques r-= rapid lyses and large plaques. ```

Question 39

Define generalized transduction

Answer 39

when the bacteriophage DNA carries a small piece of host bacterial genome due to errors in protein packaging when the parent phage originally injected their DNA in the bacterial genome. Leads to a defective phage.

Question 40

How does the process of generalized transduction allow for increasing diversity of bacteria??

Answer 40

1) the phage DNA is injected into the host cell 2) the phage DNA is replicated using the host cell machinery 3) the new phages assemble but some of the phages accidentally package bacterial dna into their heads instead of phage dna. 4) the phage containing bacterial dna will travel to another bacterial cell and inject it into the other bacteria's chromosome 5) bacterial DNA can recombine with new host's chromosome.

Question 41

what is cotransduction?

Answer 41

simultaneous transduction in 2 markers. Indicates close proximity of the genes.

Question 42

What is a temperate phage?

Answer 42

a phage that can display both the lytic and the lysogenic lifecycle. Can perform specialized transduction

Question 43

What is specialized transduction?

Answer 43

only a few specific genes can be transferred, dependent on the virus

Question 44

the lytic cycle leads to ____ transduction

Answer 44

generalized

Question 45

Lysogenic lifecucle

Answer 45

does not immediately lead to lysis of host cell. injected DNA is integrated into bacterial chromosome, becomes a prophage, and only a few genes are expressed. the DNA of the phage gets replicated everytime the bacterial cell's chromosome is replicated. therefore all progeny bacteria carry the prophage of the temperate phage

Question 46

Lysogenic life cycle leads to ____transduction

Answer 46

specialized

Question 47

Under stressful conditions, the prophage gets _____, and the lytic lifecycle begins

Answer 47

the prophage gets INDUCED (excised)

Question 48

How does gene transfer between bacteria occur by a temperate phage?

Answer 48

During improper excision. the bacterial cell might get excised instead of the prophage getting induced, and the genes get transferred to an adjacent insertion site in another bacterial chromosome, while the viral prophage gets left behind