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Microbio > Unit 3: Chapter 16 > Flashcards

Unit 3: Chapter 16 Flashcards

1
Q

Mutations

A

Heritable changes in DNA sequence

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2
Q

Point mutations

A

single nucleotide changes

Ex. Insertions or deletions

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3
Q

Spontaneous mutations

A

arise in absence of any stimulus

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4
Q

Where can spontaneous mutations result from?

A
  1. errors in DNA replication
  2. head on collisions between replisome and polymerase
  3. spontaneously occuring lesions in DNA
  4. action of mobile genetic elements
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5
Q

What are examples of spontaneous mutations?

A

Insertion, deletion, transititon, transversion

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6
Q

Tautomerization

A

Nitrogenouse base of nucleotide shifts to tautomeric form which allows for unique base pairing to occur (2 or more interconvertible structures)

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7
Q

Transition mutation

A

Stable change of nucleotide sequence from purine to purine or pyrimidine to pyrmidine

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8
Q

The shape of purine with purine is

A

Too wide

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9
Q

Transversion mutation

A

Changes of nucleotide sequence from purine to pyrmidine which causes steric problems

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10
Q

The shape of pyrimidine with pyrimidine is

A

Too narrow

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11
Q

Insertions

A

Occurs at short stretches of repeated nucleotides (AT) and slippage in synthesizing new daughter strand

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12
Q

What is the shape for purione with pyrimidine?

A

Normal base pairing

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13
Q

Deletions

A

Occurs at short stretches of repeated nucleotides (AT) and slippage in parental old strand

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14
Q

Spontaneous occuring lesions in DNA

A
  • Purines lose their base (depurinated) while the phosphate sugar backbone remains intact
  • Forms apurinic site which cannot base pair and may cause mutation after next round of replication
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15
Q

Induced mutations

A

Results of exposure to mutagen which can be physical/ chemical agents that damage DNA

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16
Q

Base analogs

A
  • Example of chemical induced mutagen
  • Structurally similiar to normal bases and mistakes occurs when they are incorporated into growing polynucleotide chain
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17
Q

This is an example of what: 5- Bromouracil is base analogue of thymine that undergoes tautomeric shift more frequently than normal base

A

Base Analogs

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18
Q

DNA modifying agents

A

Alter a base causing it to mispair

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19
Q

This is an example of what: methyl-nitrosoguanidine adds methyl groups to guanine causing it to mispair with thymine

A

DNA modifying agents

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20
Q

Intercalating agents

A
  • distort DNA to induce single nucleotide pair insertions and deletions
  • mutagens are planar and insert themselves between stacked bases of helix
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21
Q

This is an example of what: ethidium bromide intercalcates in DNA and use as stain

A

Intercalcating agents

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22
Q

Ultraviolet radiation

A

thymine dimers between 2 thymine bases on the same strand

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23
Q

Wildtype

A

The most prevalent form of gene and its associated phenotype

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24
Q

Forward mutation

A

Wild type to mutant form

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25
Q

Reverse mutation

A

Mutant phenotype to wild type phenotype

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26
Q

Supressor mutation

A

Wild type phenotype is restored at a different site than original mutation

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27
Q

Where are mutations?

A

in regulatory or coding sequences in tRNA and rRNA genes

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28
Q

Silent mutation

A

change nucleotide sequence of codon but not amino acid
(minimal effect)

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29
Q

Missense mutation

A

Single base substitution that changes codon for one amino acid into codon for another amino acid

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30
Q

Nonsense mutation

A

Converts sense codon to nonsense (STOP: TAG, TGA, TAA) codon
(early stop)

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31
Q

Frameshift mutation

A

Results from insertion or deletion of base piars in coding region of gene
(can be most detrimental)

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32
Q

Proofreading

A
  • 1st defense of DNA repair
  • Fix mistakes in base pairing by DNA polymerase
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33
Q

Mismatch repair

A
  • Mismatch correction enzyme scans newly synthesized DNA for mismatched pairs
  • Mismatched pairs are removed and replaced by DNA polymerase
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34
Q

DNA methylation

A
  • Parental DNA is methylated and new DNA temporarily lacks methyl groups
  • Repair system cuts out the mismatch from unmethylated strand
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35
Q

Excision Repair

A

corrects damage that distorts the DNA double helix by removing damaged DNA

36
Q

Nucleotide excision repair

A

Removes thymine dimers or other injury that produces distorted DNA

37
Q

Base excision repair

A

Removes damaged or unnatural bases yielding apurinic/ apyrimidic (AP) sites

38
Q

Photoreactivation

A
  • direct repair to directly split thymine dimers and light is required
  • catalyzed by photolyase
39
Q

Recombinational Repair

A
  • Corrects DNA that has both bases of a pair missing or damaged
  • Uses RecA
40
Q

SOS response

A

Global control network for repair
Used when damage is SO GREAT that normal repair mechanisms won’t work

41
Q

SOS response activation

A

RecA protein initiates recombindation repair and acts as protease to destroy LexA to increase production of excision repair enzymes
RecA protein initiates recombination pair by activating over 50 genes

42
Q

Recombination

A

Process in which one or more nucleic acids are rearranged or combined to produce new nucleotide sequences
(INCREASE IN GENETIC VARIANCE)

43
Q

Vertical gene transfer

A

Transfer of genes from parents to progeny

44
Q

Examples of vertical gene transfer

A

Asexual reproduction by microorganisms
Sexual reproduction by eukaryotes

45
Q

Horizontal Gene Transfer

A

Genes from one independent mature organism to another

46
Q

Mechanisms of Horizontal Gene Transfer

A

Transformation, Conjugation, Transduction

47
Q

Transformation

A

DNA aquired directly from environment

48
Q

Conjugation

A

DNA transfered from a donor cell

49
Q

Transduction

A

DNA transported in a bacteriophage

50
Q

4 Fates of DNA in recepient

A
  1. Integration
  2. Separate existence of DNA
  3. Remains in cytoplasm
  4. Degradation
51
Q

Homologous recombination

A

carried out by RecA proteins and double strand break occurs for crossing over

52
Q

Site specific recombination

A

Does not require long sequence homology
Recombination at specific target sites and uses recombinase

53
Q

Transposable elements

A

Genetic elements that move within or between genomes
(JUMPING GENES)

54
Q

Simple Transposition

A

Cut and Paste
Transposase catalyzes
Genes jump into different place

55
Q

Replicative transposition

A

Copy gene and 2 places with same gene
Mobile genetic element remains at og site

56
Q

Conjugative plasmids

A

Independent from chromosomes and has own genes for conjugation

57
Q

F Factor

A

Fertility fator
Have genes for cell attachment and plasmid transfer between E. Coli cells

58
Q

Episome

A

Can exist outside chromosome or be integrated

59
Q

J. Lederberg and E. Tatum

A

Incubated 2 auxotrophs bacteria together and noticed recombination

60
Q

B. Davis

A

U tube experiment that kept cells separate showed as gene transfer
(Showed cell to cell contact must be required)

61
Q

W. Hayes

A

Gene transfer during conjugation was unidirectional transfer (donor to recepient)

62
Q

F+ x F- =

A

F+

63
Q

Sex Pilus

A

Used to establish contact between F+ and F- cells

64
Q

During F+ and F- mating what happens?

A

Direct cell to cell required
Plasmid only transfered not chromosomal DNA

65
Q

Rolling circle replication

A

Mode of DNA replication in which replication fork moves around a circular DNA molecule, displacing a strand to give a 5’ tail that is also copied to produce new double strand DNA

66
Q

Hfr strain

A

Donor and contains F factor integrated into their chromosome

67
Q

Hfr x F- =

A

F-

68
Q

F- x F- =

A

F’

69
Q

F. Griffith

A

Discovered transformation

70
Q

Natural transformation

A

Bacteria lyse and release DNA into environmet

71
Q

During natural transformation, DNA has to come in contact with what to be imported

A

Competent cells

72
Q

Natural transformation of Streptococus pheomoniae

A

Becomes competent during exponential phase of bacterial growth

73
Q

Natural transformation of Bacillus subtillus

A

Becomes competent during stationary phase of bacterial growth

74
Q

Natural transformation of Haemophilus Influenzae

A

Takes up DNA only from closely related species

75
Q

Artificial Transformation

A

Lab technique that induces cels to take up DNA and used for cells not naturally competent (Ex. E. Coli)

76
Q

Bacteriophages

A

Bacterial viruses

77
Q

Virulent bacteriophages

A

Can carry out lytic cycle

78
Q

Temperant bacteriophages

A

Lysogen which is insertion of viral genome into bacterial chromosome

79
Q

Generalized transduction

A

Any part of bacterial genome can be transferred

80
Q

Specialized transduction

A

Errors in lysogenic cycle insert genomes into specific site in host chromosome

81
Q

Origin of drug resistance from

A

Immunity genes and Horizontal Gene Transfer

82
Q

Immunity Genes

A

Resistance genes in nature

83
Q

Horizontal gene transfer drug resistance

A

Transfer immunity genes from antiobiotic producers to nonproducing microbes

84
Q

Where can resistance genes be found?

A

Bacterial chromosome, plasmids, transposons, other mobile genetic elements

85
Q

R (resistance) plasmid

A

can be transferred by horizontal gene transfer
genes code for enzymes that destroy or modify drugs

86
Q

Movement of antibiotic resistance genes through

A

Conjugative transposons

Microbio (18 decks)

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