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BIOL 2330 - microbiology > microbial genetics > Flashcards

microbial genetics Flashcards

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1
Q

what is horizontal gene transfer

A

genes are passed laterally from one mature prokaryote to another

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2
Q

what type of organisms can undergo HGT

A

prokaryotes

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3
Q

what is a recombinant organism

A

one that has characteristics of both the donor and recipient

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4
Q

what is the main method of genetic diversity among prokaryotes

A

HGT

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5
Q

what types of DNA can be transferred in HGT

A

a DNA fragment or a plasmid

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6
Q

list the 3 methods in which HGT can occur

A

conjugation, transformation, transduction

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7
Q

what are the 2 possible fates for HGT

A

either you get stable recombinants or no stable recombinants

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8
Q

what 2 ways can we get stable recombinants due to HGT

A

if the DNA is integrated into the host chromosome or if the donor DNA self replicates into a plasmid

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9
Q

what 2 ways do we get no stable recombinants due to HGT

A

when the donor DNA cannot self replicate, or when there’s degradation of donor DNA

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10
Q

define conjugation

A

transfer of genetic material from a donor cell to a recipient cell via direct contact

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11
Q

what is conjugation mediated by

A

the F plasmid

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12
Q

what does the F plasmid stand for

A

fertility plasmid

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13
Q

how many stands do plasmids have

A

2

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14
Q

shape of plasmids?

A

linear or circular

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15
Q

do plasmids have lots of few genes

A

few

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16
Q

describe the importance of plasmids in regards to the host genome

A

plasmids are seen as “extra” for the host

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17
Q

describe the number of copies that plasmids can exist as

A

can be single or multicopy

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18
Q

define episome

A

a plasmid that can exist with or without being incorporated into the host’s chromosome

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19
Q

T or F: the F plasmid is an episome

A

true

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20
Q

what are cells that carry the F plasmid called

A

F+ (donor)

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21
Q

what are cells that lack the F plasmid called

A

F- (recipient)

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22
Q

what do F+ cells produce to aid in conjugation

A

sex pili

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23
Q

what type of bacteria is the F plasmid found in

A

only gram negative

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24
Q

T or F: the F plasmid is found in all types of bacteria (both gram neg and pos)

A

false; only gram negative

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25
Q

describe conjugation briefly

A

donor cell protrudes the sex pilus and contact is made with the recipient cell. F plasmid goes through the sex pilus into the recipient cell and then the pilus retracts

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26
Q

in terms of F+ and F-, describe the final result of an F+ cell conjugating with an F- cell

A

both cells become F+

27
Q

describe how the F plasmid can be incorporated onto the recipient’s chromosome

A

plasmid contains sequences that are homologous to sequences on the chromosome, thus homologous recombination can occur (plasmid insertion)

28
Q

what is homologous recombination

A

plasmid integrates into the host’s chromosome due to homologous sequences

29
Q

what is an Hfr cell (how is it made)

A

made when a bacterium gets the F plasmid integrated into it’s chromosome

30
Q

where is the plasmid DNA from the donor located in an Hfr cell

A

plasmid DNA has been incorporated into the chromosome

31
Q

what does Hfr stand for

A

high frequency of recombination

32
Q

what happens when an Hfr cell and F- cell conjugate

A

the chromosome breaks before the entire thing has transferred and the F plasmid is not transferred. F- remains as such, though it can contain new chromosomal genes

33
Q

result of Hfr x F-

A

Hfr and F-

34
Q

T or F: an integrated F plasmid may hop out of the Hfr chromosome

A

true

35
Q

what can happen when the integrated F plasmid hops out of the Hfr chromosome

A

a mistake in excision may occur, and it may carry some of the donor’s chromosomal genes with it

36
Q

what is produced when the integrated F plasmid leaves the Hfr chromosome + takes donor genes with it

A

we get F’ (F prime)

37
Q

what do we get when F’ x F-

A

F’ and F’

38
Q

T or F: conjugation can occur in both gram neg and gram pos bacteria

A

true; but there are some differences

39
Q

list 1 difference in gram pos conjugation vs gram neg conjugation

A

gram pos conjugation does not involve a sex pilus

40
Q

define transformation

A

the uptake of DNA from the environment

41
Q

what two forms of DNA can be used in transformation

A

DNA fragment or a plasmid

42
Q

what are competent cells

A

a cell that’s in a physiological state in which it can uptake donor DNA

43
Q

in what environments might transformation occur (4)

A

soil, water, in vivo, biofilms

44
Q

how does transformation work

A

a pilus extends into the environment and retracts back into the cell when it contacts DNA

45
Q

are E coli cells naturally competent

A

no

46
Q

how are e coli cells made competent in the lab

A

heat shock with CaCl or electrical shock via an electroporator

47
Q

define transduction

A

the mechanism by which bacterial genes are transferred from one bacterium to another via a bacteriophage

48
Q

what are bacteriophages

A

viruses that infect bacteria

49
Q

list the 2 types of bacteriophages

A

virulent or temperate

50
Q

what do virulent phages do/what do they do to the bacteria

A

they lyse the bacterial cell

51
Q

what do temperate phages do/what do they do to the bacteria

A
  1. can reproduce lytically
  2. can integrate into the host’s chromosome + remain with it without destroying the bacterial cell
52
Q

what is the viral genome called once the temperate phage has integrated into the host’s chromosome

A

prophage

53
Q

what is the name for the bacterium that’s harboring the temperate phage

A

lysogen

54
Q

go through the steps of the lytic cycle

A

phage injects DNA into host cell’s cytoplasm. This directs the synthesis of many new phages, then cell lyses and releases the new pathogens/phages. the phages can then bind to other cells

55
Q

go through the steps of the lysogenic cycle

A

phage injects DNA into cell and then the DNA is integrated into the host chromosome. Prophage DNA is copied when the cell divides. Exposure to stress (ie UV light) triggers excision from the host chromosome, and now the host chromosome is pure again

56
Q

what temperate phage infects e coli

A

bacteriophage lambda

57
Q

what are the two types of transduction

A

general and specialized

58
Q

when does general transduction occur (what cycle)

A

during the lytic cycle

59
Q

what types of phages use general transduction

A

both virulent and temperate

60
Q

describe general transduction

A

random pieces of DNA are transferred from one bacterium to another via a phage. Any piece of the host’s chromosome can be transferred = generalized

61
Q

when does specialized transduction occur

A

when there is an error in the life cycle of a temperate phage

62
Q

why is specific transduction called specific

A

only specific pieces of DNA from the host will be transferred to the recipient via a phage

63
Q

describe how HGT can be responsible for the spread of antibiotic resistance

A

microbes that synthesize antibiotics must have resistance genes. these genes are spread via HGT to other cells, giving them resistance too. OR spontaneous mutations may occur but less likely

BIOL 2330 - microbiology (30 decks)

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