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BIOL-2301 Final Exam > Chapter 9: Genetics of Bacteria and Their Viruses > Flashcards

Chapter 9: Genetics of Bacteria and Their Viruses Flashcards

1
Q

What is mobile DNA?

A

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

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2
Q

Do bacterial cells undergo meiosis?

A

no, they have haploid and diploid lifecycle stages

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3
Q

Define prototrophic

A

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

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4
Q

can a prototrophic bacteria grow on MM?

A

yes, it can make everything it needs

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5
Q

Define auxotrophic

A

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

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6
Q

can an auxotrophic bacteria grow on MM?

A

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

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7
Q

What is a carbon source mutant?

A

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-)

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8
Q

Transformation

A

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.

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9
Q

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

A

competency

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10
Q

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

A

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

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11
Q

What is cotransformation?

A

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.

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12
Q

The F+ factor is located in the ____ cell

A

donor cell

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13
Q

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

A

Hfr cell. high frequency of recombination.

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14
Q

What is an episome?

A

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

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15
Q

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

A

all cells become F+

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16
Q

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

A

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

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17
Q

What is conjugation?

A

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

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18
Q

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

A

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

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19
Q

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

A

conjugation bridge

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20
Q

How does DNA replicate in a bacterial cell undergoing conjugation?

A

ROLLING CIRCLE REPLICATION.

21
Q

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

A

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.

22
Q

How does conjugation aid in recombination?

A

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.

23
Q

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

A

single strand.

24
Q

Outline the process of Hfr transfer.

A

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-

25
Q

What is interrupted mating?

A

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

26
Q

What is the standard interruption mating pairs?

A

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

27
Q

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

A

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.

28
Q

what is “time of entry”

A

time where no recombinants were detected.

29
Q

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

A

true, they will eventually plateau though.

30
Q

What is an F’ factor?

A

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.

31
Q

What is transduction?

A

transfer of bacterial genes between bacterial cells mediated by viruses.

32
Q

T/F: bacteriophages are obligate parasites

A

true

33
Q

Describe the Lytic life cycle of a bacteriophage

A

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

34
Q

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

A

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

35
Q

What is a host range

A

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

36
Q

How can you characterize phage genomes?

A

using plaque size characterization and host ranges

37
Q

What is bacteriophage mixed infection?

A

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

38
Q

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

A 
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.
39
Q

Define generalized transduction

A

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.

40
Q

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

A

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.

41
Q

what is cotransduction?

A

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

42
Q

What is a temperate phage?

A

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

43
Q

What is specialized transduction?

A

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

44
Q

the lytic cycle leads to ____ transduction

A

generalized

45
Q

Lysogenic lifecucle

A

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

46
Q

Lysogenic life cycle leads to ____transduction

A

specialized

47
Q

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

A

the prophage gets INDUCED (excised)

48
Q

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

A

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

BIOL-2301 Final Exam (6 decks)

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