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Genetics > Exam 2 (Ch.15- Mutations) > Flashcards

Exam 2 (Ch.15- Mutations) Flashcards

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1
Q

a heritable change in the genetic material & provide allelic variations

A

Mutation

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2
Q

3 types of mutations

A
  1. chromosome mutations
  2. genome mutations
  3. single-gene mutations
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3
Q

mutations in the DNA resulting from an agent: UV, radiation, chemicals

A

induced mutations

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4
Q

random change in the DNA due to errors in replication that occur without known cause

A

spontaneous mutations

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5
Q
  • Changes in chromosome structure
  • Ex: huge deletions of chromosomes
A

Chromosome mutations

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6
Q
  • Changes in chromosome number
  • Ex: Trisomy 21
A

Genome Mutations

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7
Q
  • Relatively small changes in DNA structure that occur within a particular gene
A

single gene mutations

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8
Q

gene mutation in which a single base pair in DNA has been changed/ base substitution

A

point mutation

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9
Q

type of point mutation:

a change of a pyrimidine (C, T) to another pyrimidine or a purine (A, G) to another purine

A

Transition (most common)

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10
Q

type of point mutation:

a change of a pyrimidine to a purine or vice versa

A

Transversion

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11
Q

A mutation involving the addition of one or more nucleotide pairs to a gene. (detrimental when occurs closer to the 5’ end)

A

Insertion/Addition

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12
Q

A change to a chromosome in which a fragment of the chromosome is removed.

A

Deletion

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13
Q

A mutation that changes a single nucleotide, but does not change the amino acid created. due to degeneracy

A

silent mutation

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14
Q

A base-pair substitution that results in a codon that codes for a different amino acid.

A

missense mutation

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15
Q

A mutation that changes an amino acid codon to one of the three stop codons, resulting in a shorter and usually nonfunctional protein.

A

nonsense mutation

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16
Q

involve the addition or deletion of nucleotides in multiples of one or two

A

frameshift mutation

(This shifts the reading frame so that a completely different amino acid sequence occurs downstream from the mutation)

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17
Q

mutation that causes base substitutions in which one base pair is altered

A

point mutations

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18
Q

mutation that results from insertions or deletions of a base pair

A

frameshift mutations

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19
Q

Changes the wild-type genotype into some new variation (the mutant allele)

A

forward mutation

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20
Q

changes a mutant phenotype back to the wild-type phenotype

A

reverse mutation (aka reversion)

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21
Q

When a mutation alters an organism’s phenotypic characteristics

A

variant

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22
Q

Genetic changes that are harmful to an organism and decreases fitness

A

deleterious mutation

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23
Q

a gene or chromosomal mutation that influences the development of an organism in such a way that the organism cannot survive

A

lethal mutation

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24
Q

any change to the genetic code that results in noticeable physiological changes that are of benefit to the organism

A

Beneficial Mutation

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25
Q

a mutant whose phenotype depends on the environmental conditions, such as a temperature-sensitive mutant (most common)

A

conditional mutants

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26
Q

upstream 5’ end before the open reading frame/specific region of a gene where RNA polymerase can bind and begin transcription. –> a mutation may alter the sequence

A

Promoter

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27
Q

make the promoter more like the consensus sequence
- may increase the rate of transcription

A

up promoter mutation

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28
Q

mutations make the promoter less like the consensus sequence
- may decrease the rate of transcription

A

down promoter mutation

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29
Q

may alter the ability of pre-mRNA to be properly spliced (introns get spliced)

A

splice recognition sequence

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30
Q

A large complex made up of proteins and RNA molecules that splices RNA by interacting with the ends of an RNA intron, releasing the intron and joining the two adjacent exons.

A

spliceosome

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31
Q

produce neither adverse or helpful changes =, in humans the vast majority of all mutations occur in the large portions of the genome that do not contain genes and therefore have no effect on gene products

A

neutral mutations

32
Q

no gene function (no gene product or non-functional product)
- usually recessive but can be dominant

A

null mutation

33
Q
  • reduced gene function ( protein retains part of its activity)
  • usually recessive but can be dominant
A

hypomorphic mutation

34
Q

phenotype depends on how protein function is changed by a mutation:

  • enhanced gene function (protein functions more efficiently)
  • extremly rare
  • usually dominant
A

hypermorphic mutation

35
Q

novel gene function (proteins has novel properties or is expressed ectopically, at the wrong place or the wrong time)
- dominant

A

neomorphic mutation

36
Q

loss of function mutation

A

null, hypomorphic

37
Q

gain of function mutation

A

hypermorphic, neomorphic

38
Q

Results from abnormalities in cellular/biological processes
- errors in DNA replication
- underlying cause originates within the cell

A

spontaneous mutations

39
Q
  • Caused by environmental agents
  • Agents that alter DNA structure are called mutagens
A

induced mutations

40
Q

What is the range of frequency of mutation?

____ ___ in every 10^4 to 10^8 ___

A

1 mutation; gametes

41
Q

test demonstrated that mutations are not adaptive but occur spontaneous

A

Luria-Delbruck fluctuation

42
Q
  • studied the resistance of E. coli to bacteriophage T1
  • discovered fluctuation in number of colonies that gained resistance to T1
  • showed a non-linearization of mutation (spontaneous)
  • ton^r (T One Resistance)
A

Luria-Delbruck fluctuation

43
Q

the ____ ___ theory predicts that the number of tonr bacteria is essentially constant in different bacterial populations

A

physiological adaption

44
Q

the ____ ____ theory predicts that the number of tonr bacteria will fluctuate in different bacterial populations

  • prove this theory was better
    -conclusion: mutations arise randomly
A

spontaneous mutation

45
Q
  • Depurination (most common)
  • Deamination
  • Oxidation
  • Tautomeric shift
A

four chemical changes that cause spontaneous mutations

46
Q
  • involves the removal of a purine (G or A) from DNA
  • the covalent bond between deoxyribose and a purine is somewhat unstable
  • occasionally undergoes a spontaneous reaction with water that releases the base from the sugar
    – The site of release is the apurinic site

occurs approx. 1000 times an hour

A

depurination

(apurinic sites can be repaired)

47
Q

AP (apurinic) sites ——-> ____ (usually replaced by T)

A

transversions

48
Q
  • When Cytosine loses its amino group and becomes Uracil
  • Estimated to occur 100 times per day in every human cell
A

deamination

49
Q

Deamination:

C –> T ——> ___

A

transition

50
Q
  • DNA may suffer.. damage by the by-products of normal cellular processes
  • caused by hydrogen peroxide (H2O2), hydroxyl radicals (OH-), superoxide radicals (O2-)
A

oxidation

51
Q

Oxidation:

G –> T ——–> ___

A

Transversion

52
Q

isomers that differ in a single proton shift in the molecule, creating a change in the bonding structure of the molecule

A

tautomers

53
Q

the keto (standard) –> enol (anomalous) form of

A

thymine and guanine
- tautomers shifts

54
Q

amino (standard) –> imino (anomalous) forms of

A

cytosine and adenine
- tautomers shifts

55
Q

keto and amino tautomers shifts allow hydrogen bonding with ____ ____

  • & can result in mutations because of _____ base pairing
A

noncomplementary bases; anomalous (T to G and C to A)

56
Q

____ mutations arise from DNA damage caused by chemicals or radiation

A

induced

57
Q

3 types of chemical mutagens

A
  • Base modifiers
  • Intercalating agents
  • Base analogues
58
Q
  • Mutagens that covalently modify the structure of a nucleotide
    — ex: nitrous acid can replace amino groups with keto groups causing deamination
  • Can change cytosine to uracil and adenine to hypoxanthine
A

base modifiers

59
Q

chemical mutagens disrupt the appropriate pairing between nucleotides by ___ ____ within the DNA

– ex: nitrogen mustards and ethyl methanesulfonate EMS

A

Alkylating bases

(another way chemical mutagens disrupt the appropriate pairing between nucleotides)

60
Q
  • contain flat planar structures that intercalate themselves in the double helix
  • this distorts the helical structure and increase the rate of single-nucleotide additions/deletions resulting in frameshift
A

intercalating agents

61
Q

example of intercalating agents

A
  • acridine dyes (cause frameshift mutations by intercalates between purines and pyrimidines)
  • proflavin
62
Q
  • can substitute purines for pyrimidines during nucleic acid replication
  • become incorporated into daughter strands during DNA replication
A

base analogs

63
Q

base analogs example:
5-bromouracil is a ___

A

thymine analogue
- it can be incorporated into DNA instead of thymine

64
Q

A test used to asses the mutagenicity of compounds

  • Uses strains of Salmonella typhimurium for their increase sensitivity to mutations and their ability to reveal the presence of specific types of mutations
  • has shown many carcinogens to be strong mutagens
A

Ames test

65
Q

What are the two types of physical mutagens?

A
  • Ionizing radiation
  • non-ionizing radiation
66
Q
  • X-rays and gamma rays
  • has short wavelengths and high energy
  • can penetrate deep into biological molecules
  • can cause double-strand breaks and deletions/inversions
A

ionizing radiation

67
Q
  • includes UV light
  • has less energy
  • cannot penetrate deeply into biological molecules
  • causes the formation of cross-linked pyrimidine dimers
  • thymine dimers may cause mutations when DNA is replicated
A

nonionizing radiation

68
Q
  • prior to DNA replication
  • Corrects the DNA damage caused by UV-induced pyrimidine dimers
A

nucleotide excision repair (NER)

69
Q
  • prior to DNA replication
  • corrects damage from oxidation, deamination and alkylation of DNA bases. these bases lesions can be spontaneous or induced
A

base excision repair (BER)

70
Q

mainly post-DNA replication
- errors after proofreading by the DNA polymerase can be fixed by this mechanism

A

Mismatch repair (MMR)

71
Q

proofreading by DNA polymerase: occurs __

A
  • during DNA replication
72
Q

Deamination of cytosine can be repaired by ____

A

base-excision repair

73
Q

involves:

  • recognition of the erroneous base by DNA glycosylase
  • cutting of DNA backbone by AP endonuclease
A

base excision repair (BER)

74
Q

frequency of tautomeric forms predicts 1 transition in ____ base pairs

A

10.000

75
Q
  • Base excision repair (BER)
  • Nucleotide excision repair (NER)
  • Proofreading function of DNA polymerase
  • Mismatch repair (MMR)
A

repair mechanisms

76
Q
  1. Removal of the mutation & additional bases by a nuclease
  2. gap-filling by DNA polymerase
  3. sealing of the nick by DNA ligase
A

3 steps of mismatch excision repair

Genetics (17 decks)

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