Finals - Mutation Flashcards
1
Q
any heritable change in the DNA
A
mutation
2
Q
importance of mutation
A
- may have deleterious or advantageous consequences to an organism (or its descendants)
- genetic studies
- major source of genetic variation which fuels evolutionary change
3
Q
Types of mutations based on no. of bases changed
A
- point mutation
- multiple mutation
4
Q
involves a single base pair
A
point mutation
5
Q
involves two or more bp
A
multiple mutation
6
Q
point mutations
A
- base substitution
- framshift mutation
7
Q
two types of base substitution
A
- transition
- transversion
8
Q
purine to purine; pyrimidine to pyrimidine
A
transition
9
Q
purine to pyrimidine; pyrimidine to purine
A
transversion
10
Q
two types of frameshift mutation
A
- base addition
- base deletion
11
Q
frameshift to the left
A
base addition
12
Q
frameshift to the right
A
base deletion
13
Q
Types of mutation based on consequences of change in terms of amino acid sequence affected
A
- silent mutation
- neutral mutation
- missense mutation
- nonsense mutation
14
Q
results in the same amino acid
A
silent mutation
15
Q
resutls in substitution of an amino acid with similar chemical properties
A
neutral mutation
16
Q
results in substitution of a different amino acid
A
missense mutation
17
Q
results in a stop codon
A
nonsense mutation
18
Q
process of altering an organism’s genetic information, which can occur naturally or through a variety of experimental technique
A
Mutagenesis
19
Q
Two types of mutagenesis
A
- spontaneous
- induced
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
21
Q
occurs as a result of interaction of DNA with an outside agent or mutagen
A
induced mutagenesis
22
Q
anything that causes mutation
A
mutagen
23
Q
Different spontaneous mutations
A
- uncorrected mismatches
- tautomerization
- replication slippage
- spontaneous depurination
- spontaneous deamination
24
Q
Errors during DNA synthesis, if uncorrected, give rise to mutations in the next round of replication.
A
uncorrected mismatches
25
- 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
tautomerization
26
Two types of tautomerization
1. keto (C=O) <-> enol (C=OH)
2. amino (NH2) <-> imino (NH)
27
DNA base pairing in tautomeric state
1. A-C
2. T-G
3. G-T
4. C-A
28
- in template DNA with short repeated sequences
- results in frameshift mutation
- happens when either template/new DNA loops out
replication slippage
29
cause of replication slippage
when either template/new DNA loops out
30
looping out of new strand
one base insertioin on new strand
31
looping out of template strand
one base deletion on new strand
32
- 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
Spontaneous Depurination
33
site formed in spontaneous depurination
apurinic site
34
- hydrolytic removal of amino (-NH2) groups from guanine (most common), cytosine or adenine
- Oxidative damage of deoxyribose with any base, but most commonly purines
Spontaneous Deamination
35
bases where deamination can occur
- guanine
- cytosine
- adenine
36
Three types of induced mutations
1. chemical mutagens
2. physical mutagens
3. transposable elements
37
chemical mutagens
1. base analogs
2. base-modifying agents
3. intercalating agents
38
physical mutagens
1. UV radiation
2. ionizing radiation
3. heat
39
Three different ways mutagens can cause mutations
1. act as base analogs
2. react directly w/ DNA
3. act directly on DNA
40
- bases that are similar enough to the standard bases to be incorpoated into nucleotides during DNA replication
- cause point mutations
base analogs
41
example of base analogs
1. 5-bromouracil
2. 2-aminopurine
42
5-bromouracil
analog of T
43
2-aminopurine
analog of A
44
5-bromouracil keto form binds with ?
adenine
45
5-bromouracil enol form binds with ?
guanine
46
2-aminopurine amino form binds with ?
thymine
47
2-aminopurine imino form binds with ?
cytosine
48
chemicals that actually change the chemical structure of certain nucleotides (bases) in DNA causing them to mis-pair
Base-modifying agents
49
Different base-modifying agents
1. deaminating agents
2. hydroxylating agents
3. alkylating agents
50
example of deaminating agents
1. nitrous acid (inorganic air pollutant)
2. sodium bisulfite (food additive)
3. sodium dioxide (burning coal and petroleum)
51
deaminate A, C, G
nitrous acid
52
deaminate C
- sodium bisulfite
- sodium dioxide
53
addition of OH
hydroxylating agents
54
add OH to cysteine
hydroxylamine
55
alkylate guanine causing frameshift mutation
1. ethylmethane sulfonate (EMS)
2. methylmethane sulfonate (MMS)
56
where are ethylmethane sulfonate (EMS) and methylmethane sulfonate (MMS) found
air polluted with cigarette smoke
57
nitrous acid effect on guanine
becomes xanthine (pairs w/ C)
58
nitrous acid effect on cytosine
becomes uracil (pairs w/ A)
59
nitrous acid effect on adenine
becomes hypoxanthine (pairs w/ C)
60
hydorxylamine effect on cytosine
becomes hydroxylaminocytosine (binds w/ A)
61
methylmethane sulfonate (MMS) effect on guanine
becomes O^6-methylguanine (pairs w/ T)
62
- thin, plate-like hydrophobic molecules that insert between adjacnt base pairs
- distortions in the helix and no unwinding
intercalating agents
63
where do intercalating agents insert
between adjacent base pairs
64
eg. of intercalating agents
1. ethidium bromide
2. proflavin
3. acridine orange
4. benzypyrene
65
intercalating agent on template strand
frameshift mutation due to insertion of one base pair
66
intercalating agent on new strand
intercalating agent lost in replication of template strand
67
- dimerization of adjacent pyrimidine bases
- 6-4 lesion
- cytosine transformation to its imine tautomer
- covalent joining of complementary strands due to interchain dimerization
UV radiation of 260 nm (UVC)
68
dimerization of adjacent pyrimidine bases
cyclobutyl dimer
69
eg. of cyclobutyl dimer
thymine dimer
70
covalent bond of thymine dimer
- C6-C6
- C5-C5
71
(6-4) lesion
6-4 photoproduct
72
what happens in (6-4) lesion
C6 covalently bonds with C4
73
effect of (6-4) lesion
1. distors helix as DNA bases are pulled closer
2. extensive cleavage of H-bonds
3. inhibits advance of replication fork
74
covalent joining of complementary strand is due to ?
interchain dimerization
75
Effects of UV radiation
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
- x-rays, gamma rays, high speed e- or alpha paricles
- fast moving neutrons
- more potent than UV
ionizing radiation
77
what are the ionizing radiations
1. x rays
2. gamma rays
3. high speed e-/alpha particles
78
effects of ionizing radiation
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
- 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
heat
80
what is resulted in heat
baseless sites (apurinic/apyrimidinic site)
81
why is heat not normally mutagenic
due to effective system for repairing nicks
