Finals - Mutation Flashcards

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1
Q

any heritable change in the DNA

A

mutation

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2
Q

importance of mutation

A
  1. may have deleterious or advantageous consequences to an organism (or its descendants)
  2. genetic studies
  3. major source of genetic variation which fuels evolutionary change
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3
Q

Types of mutations based on no. of bases changed

A
  1. point mutation
  2. multiple mutation
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4
Q

involves a single base pair

A

point mutation

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5
Q

involves two or more bp

A

multiple mutation

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6
Q

point mutations

A
  1. base substitution
  2. framshift mutation
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7
Q

two types of base substitution

A
  1. transition
  2. transversion
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8
Q

purine to purine; pyrimidine to pyrimidine

A

transition

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9
Q

purine to pyrimidine; pyrimidine to purine

A

transversion

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10
Q

two types of frameshift mutation

A
  1. base addition
  2. base deletion
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11
Q

frameshift to the left

A

base addition

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12
Q

frameshift to the right

A

base deletion

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13
Q

Types of mutation based on consequences of change in terms of amino acid sequence affected

A
  1. silent mutation
  2. neutral mutation
  3. missense mutation
  4. nonsense mutation
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14
Q

results in the same amino acid

A

silent mutation

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15
Q

resutls in substitution of an amino acid with similar chemical properties

A

neutral mutation

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16
Q

results in substitution of a different amino acid

A

missense mutation

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17
Q

results in a stop codon

A

nonsense mutation

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18
Q

process of altering an organism’s genetic information, which can occur naturally or through a variety of experimental technique

A

Mutagenesis

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19
Q

Two types of mutagenesis

A
  1. spontaneous
  2. induced
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20
Q
  • occurs as a result of natural processes in cells
  • could be due to evasion of proofreading by DNA pol I
A

spontaneous mutagenesis

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21
Q

occurs as a result of interaction of DNA with an outside agent or mutagen

A

induced mutagenesis

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22
Q

anything that causes mutation

A

mutagen

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23
Q

Different spontaneous mutations

A
  1. uncorrected mismatches
  2. tautomerization
  3. replication slippage
  4. spontaneous depurination
  5. spontaneous deamination
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24
Q

Errors during DNA synthesis, if uncorrected, give rise to mutations in the next round of replication.

A

uncorrected mismatches

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25
Q
  • proton shift
  • bases of DNA are capable of existing in two forms by which they interconvert
  • occurs when the tautomeric form of a base pairs with a non-complementary base, which becomes fixed in the DNA sequence after replication
A

tautomerization

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26
Q

Two types of tautomerization

A
  1. keto (C=O) <-> enol (C=OH)
  2. amino (NH2) <-> imino (NH)
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27
Q

DNA base pairing in tautomeric state

A
  1. A-C
  2. T-G
  3. G-T
  4. C-A
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28
Q
  • in template DNA with short repeated sequences
  • results in frameshift mutation
  • happens when either template/new DNA loops out
A

replication slippage

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29
Q

cause of replication slippage

A

when either template/new DNA loops out

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30
Q

looping out of new strand

A

one base insertioin on new strand

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31
Q

looping out of template strand

A

one base deletion on new strand

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32
Q
  • loss of purine bases (adenine and guanine) from DNA.
  • N-glycosyl bond to deoxyribose is broken by hydrolysis, leaving the DNA’s sugar–phosphate chain intact, producing an abasic site
A

Spontaneous Depurination

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33
Q

site formed in spontaneous depurination

A

apurinic site

34
Q
  • hydrolytic removal of amino (-NH2) groups from guanine (most common), cytosine or adenine
  • Oxidative damage of deoxyribose with any base, but most commonly purines
A

Spontaneous Deamination

35
Q

bases where deamination can occur

A
  • guanine
  • cytosine
  • adenine
36
Q

Three types of induced mutations

A
  1. chemical mutagens
  2. physical mutagens
  3. transposable elements
37
Q

chemical mutagens

A
  1. base analogs
  2. base-modifying agents
  3. intercalating agents
38
Q

physical mutagens

A
  1. UV radiation
  2. ionizing radiation
  3. heat
39
Q

Three different ways mutagens can cause mutations

A
  1. act as base analogs
  2. react directly w/ DNA
  3. act directly on DNA
40
Q
  • bases that are similar enough to the standard bases to be incorpoated into nucleotides during DNA replication
  • cause point mutations
A

base analogs

41
Q

example of base analogs

A
  1. 5-bromouracil
  2. 2-aminopurine
42
Q

5-bromouracil

A

analog of T

43
Q

2-aminopurine

A

analog of A

44
Q

5-bromouracil keto form binds with ?

A

adenine

45
Q

5-bromouracil enol form binds with ?

A

guanine

46
Q

2-aminopurine amino form binds with ?

A

thymine

47
Q

2-aminopurine imino form binds with ?

A

cytosine

48
Q

chemicals that actually change the chemical structure of certain nucleotides (bases) in DNA causing them to mis-pair

A

Base-modifying agents

49
Q

Different base-modifying agents

A
  1. deaminating agents
  2. hydroxylating agents
  3. alkylating agents
50
Q

example of deaminating agents

A
  1. nitrous acid (inorganic air pollutant)
  2. sodium bisulfite (food additive)
  3. sodium dioxide (burning coal and petroleum)
51
Q

deaminate A, C, G

A

nitrous acid

52
Q

deaminate C

A
  • sodium bisulfite
  • sodium dioxide
53
Q

addition of OH

A

hydroxylating agents

54
Q

add OH to cysteine

A

hydroxylamine

55
Q

alkylate guanine causing frameshift mutation

A
  1. ethylmethane sulfonate (EMS)
  2. methylmethane sulfonate (MMS)
56
Q

where are ethylmethane sulfonate (EMS) and methylmethane sulfonate (MMS) found

A

air polluted with cigarette smoke

57
Q

nitrous acid effect on guanine

A

becomes xanthine (pairs w/ C)

58
Q

nitrous acid effect on cytosine

A

becomes uracil (pairs w/ A)

59
Q

nitrous acid effect on adenine

A

becomes hypoxanthine (pairs w/ C)

60
Q

hydorxylamine effect on cytosine

A

becomes hydroxylaminocytosine (binds w/ A)

61
Q

methylmethane sulfonate (MMS) effect on guanine

A

becomes O^6-methylguanine (pairs w/ T)

62
Q
  • thin, plate-like hydrophobic molecules that insert between adjacnt base pairs
  • distortions in the helix and no unwinding
A

intercalating agents

63
Q

where do intercalating agents insert

A

between adjacent base pairs

64
Q

eg. of intercalating agents

A
  1. ethidium bromide
  2. proflavin
  3. acridine orange
  4. benzypyrene
65
Q

intercalating agent on template strand

A

frameshift mutation due to insertion of one base pair

66
Q

intercalating agent on new strand

A

intercalating agent lost in replication of template strand

67
Q
  • dimerization of adjacent pyrimidine bases
  • 6-4 lesion
  • cytosine transformation to its imine tautomer
  • covalent joining of complementary strands due to interchain dimerization
A

UV radiation of 260 nm (UVC)

68
Q

dimerization of adjacent pyrimidine bases

A

cyclobutyl dimer

69
Q

eg. of cyclobutyl dimer

A

thymine dimer

70
Q

covalent bond of thymine dimer

A
  • C6-C6
  • C5-C5
71
Q

(6-4) lesion

A

6-4 photoproduct

72
Q

what happens in (6-4) lesion

A

C6 covalently bonds with C4

73
Q

effect of (6-4) lesion

A
  1. distors helix as DNA bases are pulled closer
  2. extensive cleavage of H-bonds
  3. inhibits advance of replication fork
74
Q

covalent joining of complementary strand is due to ?

A

interchain dimerization

75
Q

Effects of UV radiation

A
  1. dimerization of adjacent pyrimidine bases
  2. (6-4) lesion
  3. cytosine to imine tautomer (pairs w/ A)
  4. covalent joining of complementary strands due to interchain dimerization
76
Q
  • x-rays, gamma rays, high speed e- or alpha paricles
  • fast moving neutrons
  • more potent than UV
A

ionizing radiation

77
Q

what are the ionizing radiations

A
  1. x rays
  2. gamma rays
  3. high speed e-/alpha particles
78
Q

effects of ionizing radiation

A
  1. formation of rare tautomeric enols
  2. removal of cytosine from DNA
  3. favored formation of the imine tautomer of C
  4. production of ss and ds breaks on DNA backbone
79
Q
  • stimulates water-induced cleavage of the β-Nglycosidic bond
  • results in baseless site causing frameshift mutation to the right
  • not normally mutagenic because cells have effectiv system for repairing nicks
A

heat

80
Q

what is resulted in heat

A

baseless sites (apurinic/apyrimidinic site)

81
Q

why is heat not normally mutagenic

A

due to effective system for repairing nicks