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
Reverse mutation
Mutant phenotype to wild type phenotype
26
Supressor mutation
Wild type phenotype is restored at a different site than original mutation
27
Where are mutations?
in regulatory or coding sequences in tRNA and rRNA genes
28
Silent mutation
change nucleotide sequence of codon but not amino acid (minimal effect)
29
Missense mutation
Single base substitution that changes codon for one amino acid into codon for another amino acid
30
Nonsense mutation
Converts sense codon to nonsense (STOP: TAG, TGA, TAA) codon (early stop)
31
Frameshift mutation
Results from insertion or deletion of base piars in coding region of gene (can be most detrimental)
32
Proofreading
- 1st defense of DNA repair - Fix mistakes in base pairing by DNA polymerase
33
Mismatch repair
- Mismatch correction enzyme scans newly synthesized DNA for mismatched pairs - Mismatched pairs are removed and replaced by DNA polymerase
34
DNA methylation
- Parental DNA is methylated and new DNA temporarily lacks methyl groups - Repair system cuts out the mismatch from unmethylated strand
35
Excision Repair
corrects damage that distorts the DNA double helix by removing damaged DNA
36
Nucleotide excision repair
Removes thymine dimers or other injury that produces distorted DNA
37
Base excision repair
Removes damaged or unnatural bases yielding apurinic/ apyrimidic (AP) sites
38
Photoreactivation
- direct repair to directly split thymine dimers and light is required - catalyzed by photolyase
39
Recombinational Repair
- Corrects DNA that has both bases of a pair missing or damaged - Uses RecA
40
SOS response
Global control network for repair Used when damage is SO GREAT that normal repair mechanisms won't work
41
SOS response activation
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
Recombination
Process in which one or more nucleic acids are rearranged or combined to produce new nucleotide sequences (INCREASE IN GENETIC VARIANCE)
43
Vertical gene transfer
Transfer of genes from parents to progeny
44
Examples of vertical gene transfer
Asexual reproduction by microorganisms Sexual reproduction by eukaryotes
45
Horizontal Gene Transfer
Genes from one independent mature organism to another
46
Mechanisms of Horizontal Gene Transfer
Transformation, Conjugation, Transduction
47
Transformation
DNA aquired directly from environment
48
Conjugation
DNA transfered from a donor cell
49
Transduction
DNA transported in a bacteriophage
50
4 Fates of DNA in recepient
1. Integration 2. Separate existence of DNA 3. Remains in cytoplasm 4. Degradation
51
Homologous recombination
carried out by RecA proteins and double strand break occurs for crossing over
52
Site specific recombination
Does not require long sequence homology Recombination at specific target sites and uses recombinase
53
Transposable elements
Genetic elements that move within or between genomes (JUMPING GENES)
54
Simple Transposition
Cut and Paste Transposase catalyzes Genes jump into different place
55
Replicative transposition
Copy gene and 2 places with same gene Mobile genetic element remains at og site
56
Conjugative plasmids
Independent from chromosomes and has own genes for conjugation
57
F Factor
Fertility fator Have genes for cell attachment and plasmid transfer between E. Coli cells
58
Episome
Can exist outside chromosome or be integrated
59
J. Lederberg and E. Tatum
Incubated 2 auxotrophs bacteria together and noticed recombination
60
B. Davis
U tube experiment that kept cells separate showed as gene transfer (Showed cell to cell contact must be required)
61
W. Hayes
Gene transfer during conjugation was unidirectional transfer (donor to recepient)
62
F+ x F- =
F+
63
Sex Pilus
Used to establish contact between F+ and F- cells
64
During F+ and F- mating what happens?
Direct cell to cell required Plasmid only transfered not chromosomal DNA
65
Rolling circle replication
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
Hfr strain
Donor and contains F factor integrated into their chromosome
67
Hfr x F- =
F-
68
F- x F- =
F'
69
F. Griffith
Discovered transformation
70
Natural transformation
Bacteria lyse and release DNA into environmet
71
During natural transformation, DNA has to come in contact with what to be imported
Competent cells
72
Natural transformation of Streptococus pheomoniae
Becomes competent during exponential phase of bacterial growth
73
Natural transformation of Bacillus subtillus
Becomes competent during stationary phase of bacterial growth
74
Natural transformation of Haemophilus Influenzae
Takes up DNA only from closely related species
75
Artificial Transformation
Lab technique that induces cels to take up DNA and used for cells not naturally competent (Ex. E. Coli)
76
Bacteriophages
Bacterial viruses
77
Virulent bacteriophages
Can carry out lytic cycle
78
Temperant bacteriophages
Lysogen which is insertion of viral genome into bacterial chromosome
79
Generalized transduction
Any part of bacterial genome can be transferred
80
Specialized transduction
Errors in lysogenic cycle insert genomes into specific site in host chromosome
81
Origin of drug resistance from
Immunity genes and Horizontal Gene Transfer
82
Immunity Genes
Resistance genes in nature
83
Horizontal gene transfer drug resistance
Transfer immunity genes from antiobiotic producers to nonproducing microbes
84
Where can resistance genes be found?
Bacterial chromosome, plasmids, transposons, other mobile genetic elements
85
R (resistance) plasmid
can be transferred by horizontal gene transfer genes code for enzymes that destroy or modify drugs
86
Movement of antibiotic resistance genes through
Conjugative transposons