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MB351 > Lecture 32 Gene Transfer in Bacteria > Flashcards

Lecture 32 Gene Transfer in Bacteria Flashcards

1
Q

What are three mechanisms of genetic transfer?

A

transformation, conjugation, and transduction

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2
Q

Horizontal Gene Transfer (HGT)

A

genetic exchange between organisms of the same generation

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3
Q

Why is horizontal gene transfer helpful?

A

allows bacteria, which typically have only one chromosome (haploid), to gain genetic diversity

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4
Q

Transformation

A

a genetic transfer process by which free DNA is incorporated into a recipient cell and may bring about genetic change

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5
Q

Competent

A

a cell that is able to take up DNA and be transformed

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6
Q

How can we induce cells to be competent?

A

by using calcium chloride or by electroporation

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7
Q

What does electroporation do?

A

causes temporary holes in cell wall/cell membrane

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8
Q

What confirmations of DNA can transformation occur with?

A

DNA fragments and plasmids

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9
Q

When DNA fragment uptake occurs, what are the two possible outcomes?

A

1) the fragment is integrated by nonreciprocal recombination –> stable transformation
2) degradation of the fragment –> unsuccessful transformation

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10
Q

Plasmids

A

independently replicating elements of double stranded DNA

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11
Q

Are plasmids helpful for bacterial cells?

A

usually are non-essential genes but can be very helpful in the right conditions

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12
Q

True or False: Multiple plasmids per cell cannot occur

A

False!

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13
Q

Dissimilation plasmids

A

plasmids that encode enzymes for catabolism of unusual elements

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14
Q

Resistance factors

A

plasmids that encode resistance to various elements (for example, antibiotics or metals)

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15
Q

Virulence plasmids

A

plasmids that increase pathogenicity

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16
Q

Conjugative or F plasmids/F factors

A

plasmids that carries genes for sex pili and transfer of plasmids

17
Q

Components of F plasmids

A

1) mobile genetic elements/jumping genes
2) tra region (transfer region)

18
Q

In conjugation, what is a donor cell?

A

the bacteria with the F plasmids (male), termed F+

19
Q

In conjugation, what is an acceptor/recipient cell?

A

the bacteria with no plasmids (female), termed F-

20
Q

How does bacterial conjugation begin?

A

sex pilus draws F- cell closer, inducing mating bridge to form

21
Q

Mating bridge

A

the region of contact between the donor and recipient cells where the DNA is transferred via a pore

22
Q

Hfr cell

A

high frequency of recombination cell; when the F plasmid recombines with the chromosome

23
Q

What happens when an F- cell goes through recombination with an Hfr cell?

A

the F- cell may acquire new versions of chromosomal genes; remains an F- cell because it did not receive the complete F factor

24
Q

Lytic cycle

A

the virus replicates and lyses cell; many reproduced

25
Q

Lysogenic cycle

A

viral DNA is incorporated into host DNA; replication is delayed

26
Q

Prophage

A

viral genome integrated into host DNA (hides out)

27
Q

Transduction

A

the transfer of bacterial genes by viruses

28
Q

When does generalized transduction occur?

A

during the lytic cycle of viruses

29
Q

Generalized transduction

A

when random fragments of DNA from partially degraded host chromosomes are packaged by mistake

30
Q

What does generalized transduction use to infect another host?

A

transducing particles

31
Q

When does specialized transduction occur?

A

during the lysogenic cycle of viruses

32
Q

Specialized transduction

A

when only specific regions of chromosome located near attachment site are transduced

33
Q

What does the traducing particles carry during specialized transduction?

A

both bacterial chromosomal DNA and phage DNA

34
Q

Mobile Genetic Elements (MGEs)

A

discrete segments of DNA that move as units from one location to another within other DNA molecules and can therefore also bring about genetic change

35
Q

Insertion sequences

A

insert into another part of the genome

36
Q

Transposons

A

sequences of DNA that move around to different positions within a genome and utalize insertion sequences

37
Q

Are insertion sequences or transposons larger?

A

transposons

38
Q

What enzyme do insertion sequences and transposons encode for?

A

transposase enzyme

39
Q

What do transposons also carry (besides transposase)?

A

many genes such as antibiotic resistance

MB351 (21 decks)

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