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genetics > chapter 6 part 1 > Flashcards

chapter 6 part 1 Flashcards

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Biology 101 flashcards
1
Q

genome simplicity

A

fewer genes & fewer bases than other organisms

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2
Q

haploid genomes

A

mutations can be observed directly because there i one copy of each gene

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3
Q

short term generation times

A

can be measured in minutes

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4
Q

enormous numbers of progeny

A

allow detection of rare events

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5
Q

ease of propagation

A

bacterial culture is easy & inexpensive & takes up very little space

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6
Q

numerous heritable differences

A

mutations are easily created, identified, isolated, & manipulated for study

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7
Q

why are bacteria useful genetic models?

A

-genome simplicity
-haploid genomes
-short generation times
-enormous numbers of progeny
-ease of propagation
-numerous heritable differences

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8
Q

how many chromosomes are bacterial genomes usually composed of?

A

a single chromosome that carries mostly essential genes

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9
Q

is the bacterial chromosome usually circular or linear?

A

it is a usually circular model of double stranded DNA

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10
Q

is a bacterial chromosome big or small compared to eukaryotic genomes?

A

small
it only contains a few thousand to a few million base pairs

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11
Q

how many plasmids do bacteria usually contain?

A

one or more

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12
Q

what are plasmids

A

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

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13
Q

are plasmids usually bigger or smaller than bacterial chromosomes?

A

smaller

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14
Q

how many different kinds of plasmids are found in bacteria?

A

many different kinds of naturally occurring plasmids are found in bacteria

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15
Q

R (resistance) plasmid

A
  • carries antibiotic resistance genes that can be transferred to recipient cells
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16
Q

F (fertility) plasmid

A
  • contains genes that promote its own transfer from donors to recipients
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17
Q

what are the two types of plasmids

A
  • R (resistance) plasmid & F (fertility) plasmid
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18
Q

can plasmids replicate independently of the bacterial chromosome?

A

yes, so that the number of plasmids per cell can increase rapidly

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19
Q

high copy number plasmids

A

plasmids that replicate independently where there are 50 or more of that plasmid per cell

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20
Q

low-copy number plasmids

A

present in one or two copes per bacterial cell & usually cannot replicate independently of the bacterial chromosome

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21
Q

do low-copy number plasmids replicate independently of the bacterial chromosome?

A

no

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22
Q

what are the three ways of recombination in prokaryotes?

A

conjugation
transformation
transduction

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23
Q

conjugation

A

the transfer of replicated DNA from a donor to a recepient

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24
Q

transformation

A

the uptake of DNA from the environment

25
Q

transduction

A

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

26
Q

what does each method of recombination involve?

A

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

27
Q

which form of recombination involves physical contact transfer?

A

conjugation

28
Q

conjugation in detail

A

-the donor cell transfers some of its genetic info to a recipient cell

29
Q

in conjugation, what is the genetic info transferred through?

A

a conjugation pilus or conjugation tube

30
Q

what takes place between the donors & recipients

A

plasmid that facilitates a one-way-transfer

31
Q

what determines the ability ot act is a donor?

A

the ‘fertility factor’ or (F) factor

32
Q

do donor cells have the F factor?

A

they have the F factor so they are F+, while the recipient cells are called F- and lack an F factor

33
Q

what is conjugation controlled by?

A

genes carried on the F plasmid

34
Q

how many genes does the F factor (plasmid) encode for?

A

40 genes that control conjugation

35
Q

what do the F factor genes direct formation of and what does it do?

A

an exporter structure that will move the donor DNA into the recipient cell

36
Q

what does the relaxosome do?

A

cuts one strand of F factor DNA, which triggers DNA replication, and movement of F factor DNA to the recipient cel where its own DNA replication occurs

37
Q

what is the recipient cell called after conjugation?

A

the exoconjugant cell
it is the recipient cell with its genetic info modified by receiving DNA from the donor cell

38
Q

mechanism of conjugation 1

A
  1. a conjugation pilus forms between donor & recipient cells
  2. gene expression from the F factor produces a protein complex called the relaxosome
  3. relaxosome binds the origin of transfer (OriT) on the F factor & cleaves one phosphodiester bond on the T (transfer) strand of the F factor
  4. relaxosome partially degenerates, leaving relaxase attached to the free 5’ end of the T strand
39
Q

mechanism of conjugation 2

A

-t strand transfer across the pilus is accompanied by a process called rolling circle replication, which starts at OriT
-rolling circle replication uses non-transferred DNA strand as a template & displaces the 5’ end of the T strand, freeing it for transfer into the recipient
-the recipient cell uses the imported DNA as a template for replication, by the end of the process, both cells contain complete double-stranded F factor

40
Q

how many insertion sequence (IS) elements are there?

A

4

41
Q

A large component of the F factor consists of four _______ ________ elements

A

insertion sequence

42
Q

what are IS elements

A

moble segments of bacterial DNA that can transpose themsleves to new locations (like transposons)

43
Q

when does an episome occur?

A

when a plasmid integrates into the bacterial chromosome

44
Q

what forms an episome?

A

when circular elements like the F factor can integrate into the bacterial chromosome

45
Q

what do we call it when the plasmid e=integrates into the bacterial chromosome?

A

Hfr cells

46
Q

what does Hfr stand for

A

high frequency recombination

47
Q

is complete transfer of the bacterial chromosome in Hfr accomplished?

A

no

48
Q

what does gene transfer to recipient cells from Hfr strains occur by?

A

rolling circle replication

49
Q

can linear dna in the recipient cell re-circularize in Hfr gene transfer?

A

no

50
Q

where does homologous recombination occur?

A

between the transferred linear DNA & the circular chromosome of the recipient (Hfr gene transfer)

51
Q

what produces partial diploids?

A

F’

52
Q

what is derived from the abberant excision of the F factor from an Hfr chromosome?

A

an F’ donor bacterium that contains a functional F factor

53
Q

what does the F’ factor contain

A

all its own DNA plus a segment of the bacterial chromosome

54
Q

what are donor cells carrying an F factor called?

A

F’ cells

55
Q

exconjugants that contain a complete F’ factor called what & why?

A

partial diploids
since they contain two copies of the bacterial chromosome genes found on the F’ factor

56
Q

is the partial diploidy retained as a characteristc of the exconjugants & their descendants?

A

`yes

57
Q

what is a merozygote

A

a state when a partially diploid bacterial cell is produced

58
Q

what can partial diploids be used to do?

A

examine the mode of action of bacterial genes & their regulation

genetics (23 decks)

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