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BM330 microbiology > block a lec 3 > Flashcards

block a lec 3 Flashcards

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Biology 101 flashcards
1
Q

what is a mutation

A

heritable change in DNA seq that can lead to a change in phenotype

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2
Q

what is a mutant

A

a strain of any cell or virus differing from parental strain in genotype

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3
Q

what is a wild type strain

A

typically refers to strain isolated from nature

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4
Q

why is perfect fidelity couterproductive

A

prevents evolution

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5
Q

what are selectable mutation

A

those that give the mutant a growth advantage under certain conditions

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6
Q

what are non selectable mutations

A

those that have neither an advantage nor disadvantage

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7
Q

what is screening

A

detecting mutations by examining a large no of colonies and looking for differences

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8
Q

what are induced mutation

A

those made environmentally or deliberately

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9
Q

how can induced mutations occur

A

results from exposure to natural radiation or oxygen radicals

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10
Q

what are spontaneous mutations

A

those that occur without external intervention

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11
Q

what are point mutations

A

mutations that change only one base pair

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12
Q

what can point mutations lead to

A

single aa change in a protein and an incomplete protein

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13
Q

what is replica plating useful for

A

identifying cells with a nutritional requirement for growth
auxotroph

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14
Q

what is a silent mutation

A

does not affect aa sequence

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15
Q

what is a missense mutation

A

aa changed
polypetide altered

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16
Q

what is a nonsense mutation

A

codon becomes stop codon, polypeptide is incomplete

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17
Q

when are nonsense mutations more likely to cause damage to phenotype

A

closer the mutation is to the beginning of the polypeptide

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18
Q

what are frameshift mutations

A

deletions or insertions that result in a shift in the reading frame

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19
Q

what do frameshift mutations often result in

A

complete loss of gene function

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20
Q

what type of mutation is typically reversible

A

point mutations

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21
Q

what is reversion

A

alteration in DNA that reverses the effects of a prior mutation

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22
Q

what does revertant mean

A

strain in which original phenotype is restored

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23
Q

what are the 2 types of revertant

A

same site revertant
second site revertant

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24
Q

what is same site revertant

A

mutation is at the same site as og mutation

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25
Q

what is second site revertant

A

mutation is at a different site in the DNA

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26
Q

what is a suppressor

A

a mutation that compensates for the effect of the original function

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27
Q

what genome has higher mutation rate

A

RNA genome
1000 fold higher

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28
Q

what is one of the first tests that new drugs undergo

A

Ames test

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29
Q

what is the Ames test

A

makes practical use of bacterial mutations to detect potentially hazardous chemicals
looks for an increase in mutation of bacteria in the presense of suspected mutagen

30
Q

what is frequency of error in DNA replication

A

10^-6 to -7

31
Q

why are there new variants of the cold every year

A

because RNA pol doesnt often have proofreading abilities

32
Q

what are mutatgens

A

chemical, physical, or biological agents that increase mutation rates

33
Q

what are nucleotide base analogs

A

they resemble nucleotides and mispair nucleotides

34
Q

what can chemical mutagens induce

A

chemical modifications
nitrosoguanidine

35
Q

what are the 2 main categories of mutagenic electromagnetic radiation

A

nonionising and ionising

36
Q

example of nonionising EMR

A

UV radiation

37
Q

examples of ionising NMR

A

X rays, Gamma rays, cosmic rays

38
Q

what strongly absorbs UV

A

purines and pyrimidines

39
Q

what is one effect of UV rad

A

pyrimidine dimer

40
Q

what can be ionised and produced

A

water to produce free radicals

41
Q

what do free radicals damage

A

damage macromols in the cell

42
Q

what are the 3 types of DNA repair systems

A

direct reversal
repair of single strand damage
repair od double strand damage

43
Q

what is direct reversal

A

mutated base is still recognisable and can be repaired without referring to other strand

44
Q

what is repair of single strand damage

A

damaged DNA is removed and repaired using opposite strand as template

45
Q

what is repair of double strand damage

A

a break in DNA
requires more error prone repair mechanisms

46
Q

what system is used when DNA damage is large
(interferes with DNA rep)

A

SOS regulatory system

47
Q

what does translesion synthesis allow

A

DNA to be synthesised with no template

48
Q

what type of activity does RecA have

A

protease activity

49
Q

what is RecA induced

A

when cell senses DNA damage

50
Q

what is the role of RecA

A

to degrade LexA

51
Q

what dos LexA do

A

sits and blocks DNA repair promoters

52
Q

what is recombination

A

physical exchange of DNA between genetic elements

53
Q

what is homologous recombination

A

process that results in genetic exchange between homologous DNA from 2 different sources

54
Q

what is selective medium used for in homologous recombination

A

to detect rare genetic recombinants

55
Q

what is the only way to repair a double stranded break

A

homologous recombination

56
Q

what are transposable elements

A

discrete segments of DNA that move as a unit from one location to another within other DNA mols

57
Q

how are transposable elements moved

A

transposition

58
Q

who first observed transposition

A

barbara mcclintock

59
Q

what are the 2 main types of transposable elements

A

transposons
insertion sequences

60
Q

what are the simplest transposable elements

A

insertion sequences

61
Q

size of IS

A

~1000 nucleotides
inverted repeats are 10-50 base pairs

62
Q

where are IS found

A

in plasmids and Chr of bacteria and archaea and some bacteriophages

63
Q

how do transposase move DNA

A

between inverted repeats

64
Q

what does the insertion of a TE generate

A

duplicate target seq

65
Q

what are the 2 mechanisms of transposition

A

conservative and replicative

66
Q

what is a conservative mechanism of transpositon

A

where transposon is excised from one location and reinserted at a second location
no of transposons stays constant

67
Q

what is a replicative mechanism of transposition

A

a new copy of transposon is produced and inserted at a second location
number of transposons present doubles

68
Q

how can gene be recovered in transpositon

A

transposons can be tagged, the AMR marker

69
Q

what does it mean if a cell is capable of growing on selective med.

A

likely acquired a transposon

70
Q

what is CRIPSR

A

clustered regulatory interspaces short palindromic repeats

71
Q

how is CRISPR carried out

A

-cuts DNA, double stranded break
-repair fragment DNA and in middle as AMR marker
-homolog recombin
-mutant at that precise place can be identified from AMR marker

BM330 microbiology (5 decks)

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