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genetics > chapter 6 part 1 > Flashcards

chapter 6 part 1 Flashcards

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Biology 101 flashcards
1
Q

in what ways are bacteria useful genetic models

A
  • genome simplicity (fewer genes/bases)
  • haploid genomes
  • short generation times (min)
  • enormous numbers of progeny
  • ease of propagation
  • numerous heritable differences
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2
Q

what are bacterial genomes usually composed of

A

single chromosome, which carries mostly essential genes

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3
Q

bacterial chromosome structure

A

covalently closed circular molecule of double-stranded DNA

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4
Q

how many base pairs do bacterial genomes usually have

A

few thousand to few million

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5
Q

plasmids

A

small double-stranded circular DNA molecules containing non-essential genes

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6
Q

are plasmids smaller or larger than bacterial chromosomes

A

smaller

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7
Q

plasmids are used in a variety of ____________ _____ ______________

A

recombinant DNA applications

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8
Q

2 types of plasmids

A
  1. R (resistance) plasmid
  2. F (fertility) plasmid
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9
Q

R plasmid

A

carries antibiotic resistance genes that can be transferred to recipient cells

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10
Q

fertility plasmid

A

contains genes that promote its own transfer from donors to recipients

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11
Q

high-copy number plasmids

A

plasmids that can replicate independently of the bacterial chromosome so that the number of plasmids per cell can increase rapidly

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12
Q

low-copy number plasmids

A

present in 1/2 copies per bacterial cell and usually cannot replicate independently of the bacterial chromosome

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13
Q

3 methods of recombination in prokaryotes

A
  1. conjugation
  2. transformation
  3. transduction
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14
Q

conjugation overview

A

transfer of replicated DNA from a donor to a recipient

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15
Q

transformation overview

A

uptake of DNA from the environment

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16
Q

transduction overview

A

transfer of DNA from one bacterium to another by a viral vector

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17
Q

each method of recombination involves what

A

one-way transfer of genetic material from a donor bacterial cell to a recipient cell

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18
Q

what is the hollow tube called where genetic information is transferred in conjugation

A

conjugation pilus/tube

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19
Q

which recombination method involves the direct physical union of two bacteria

A

conjugation

20
Q

what is the ability to act as a donor determined by

A

fertility factor (F factor)

21
Q

does the donor or recipient possess an F factor

A

donor - F+ cells

22
Q

does the donor or recipient lack an F factor

A

recipient - F- cells

23
Q

what is conjugation controlled by

A

genes carried on the F plasmid

24
Q

what does the F factor plasmid control

A

40 genes that control conjugation

25
Q

what do the F factor genes direct formation of

A

exported structure that will move the donor DNA into the recipient cell

26
Q

relaxosome

A

cuts one strand of F factor DNA, triggering DNA replication, and movement of F factor DNA to the recipient cell where its own DNA replication occurs

27
Q

exoconjugant cell

A

term for the recipient cell after conjugation
- recipient cell with its genetic information modified by receiving DNA from the donor cell

28
Q

mechanism of conjugation 1

A
  • conjugation plus forms between donor/recipient cells
  • gene expression from F factor produces protein complex called relaxosome
  • relaxosome binds to origin of transfer (ori) on F factor and cleaves one phosphodiester bond on T (transfer) strand of F factor
  • relaxosome partially degenerates, leaving relaxase attached to free 5’end of T strand
29
Q

mechanism of conjugation II

A
  • relaxase facilitates movement of t strand through conjugation pilus into recipient cell
  • T strand transfer across pilus is accompanies by a specialized process called rolling circle replication
  • rolling circle replication uses non-transferred DNA strand as a template and displaces the 5’ end of T strand, freeing it for transfer into recipient
  • recipient cell uses imported DNA as template for replication
30
Q

at the end of conjugation, which cell contains a complete double-stranded F factor

A

both cells

31
Q

how many insertion sequences does a large F factor contain

A

4

32
Q

insertion sequence (IS) elements

A

mobile segments of bacterial NA that can transpose themselves to new locations (like transposons)

33
Q

episome

A

when circular elements like the F factor or plasmid integrate into the bacterial chromosome

34
Q

Hfr cells (high frequency recombination)

A

when an F factor forms an episome in bacteria

35
Q

how does gene transfer to recipient cells from Her strains occur

A

rolling circle replication (F+ x F- conjugation)

36
Q

what is not accomplished in gene transfer from Hfr cell

A

complete transfer of bacterial chromosome - it is too long

37
Q

what happens when the segment of T strand DNA enters the recipient in transfer from Hfr cell

A

used to generate a double-stranded linear fragment

38
Q

can linear DNA in the recipient cell re-circularize?

A

no

39
Q

where does homologous recombination occur?

A

between transferred linear DNA and circular chromosome of recipient

40
Q

how may the new exconjugant cell acquire 1+ donor genes?

A

homologous recombination between linear DNA and circular chromosome

41
Q

F’ cells

A

donor cells carrying and F factor derived from excision of F factor from Hfr chromosome

42
Q

F’ donor bacterium contains

A

functional F factor derived from aberrant (imperfect) excision of F factor from an Hfr chromosome)

43
Q

what does resulting F’ factor contain

A

all its own DNA plus a segment of the bacterial chromosome

44
Q

what are exconjugants that contain a complete F’ factor called

A

partial diploids

45
Q

partial diploids

A

contain 2 copies of bacterial chromosome genes found on the F’ factor

46
Q

how is partial diploidy retained

A

as a characteristic of the exconjugants and their descendants

47
Q

merozygote

A

a state when a partially diploid bacterial cell is produced

genetics (47 decks)

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