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Microbiology > Microbial Genetics > Flashcards

Microbial Genetics Flashcards

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1
Q

Define genetics

A

study of genes; how they carry information; how that info is expressed; how that info is replicated

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2
Q

Define chromosomes

A

made up of DNA and protein; contain genes

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3
Q

Define genes

A

segment of DNA that encodes for functional products ( ex. proteins)

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4
Q

Define genome

A

genetic information in the cell

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5
Q

Define genetic code

A

set of rules that determine how nucleotides sequence converted to amino acid to protein

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6
Q

Define DNA and the 2 essential functions

A

Genetic blueprint

1) stores genetic information that instructs the cells on how to make proteins ( indirectly plays a role in protein synthesis)
2) replicates and make a copy of itself; copy passed down to daughter cell

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7
Q

What is the central dogma

A

dna> rna> protein

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8
Q

Define gene expression

A

combo of transcription and translation

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9
Q

Descrine bacterial dna and chromosomes

A

single circular chromosome
dna and protein
no histone ( just histone like proteins)

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10
Q

Define short tandem repeats (STRs)

A

repeating sequences of noncoding DNA

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11
Q

What are the 2 transfers of genetic information

A

1) vertical gene transfer

2) horizontal gene transfer

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12
Q

Define vertical gene transfer

A

flow of genetic information from 1 generation to the next.

occur during reproduction from parent to offspring

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13
Q

Define horizontal gene transfer

A

specific to prokaryotes
the transfer of genes b/t cells of the same generation
transfer from the donor cell to the reciptant cell
allows for recombination cell or recombination chromosome
recombinant genetic information not same as parent

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14
Q

Define recombination

A

genetic information can be transferred b/t cells of the same generation

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15
Q

What does DNA replications result in

A

formation of 2 identical complete DNA molecules each having 1 new strand and 1 strand from the original DNA

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16
Q

Define DNA gyrase

A

enzyme that release strain in region

relaxes supercoiling ahead of the replication fork

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17
Q

Define DNA helicase

A

enzyme that seperate both strands. unwinds double stranded DNA

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18
Q

Define DNA polymerase

A

bring complementary nucleotide and bring it growing strand; check if correct nucelotide is attached; synthesizes DNA; proofread and repairs DNA

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19
Q

Define replication fork

A

structure that forms within the long helical DNA during DNA replication

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20
Q

Define semiconservative

A

replication of a nucleic acid in which one strand of each double helix is directly derived from the parent molecules

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21
Q

What direction does DNA polymerase add nucleotide

A

5 to 3 prime direction

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22
Q

What initiates dna polymerase

A

RNA primer

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23
Q

Leading strand is …

Lagging strand is…..

A

synthesized continuously

synthesized discontinuosly, creating okazaki fragments

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24
Q

What remove the RNA primers and what joins the Okazaki fragment

A

dna polymerase remove primers

DNA ligase join okazaki fragments

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25
Q

What are the 6 steps at the DNA replication fork ( figure 7.13)

A

1) enzymes unwind the parental double helix
2) proteins stabilize the unwound parental DNA
3) The leading strand is synthesized continuously by DNA polymerase
4) the lagging strand is synthesized discontinously. Primase, an RNA polymerase, synthesized a short RNA primer, which is then extended by DNA polymerase
5) DNA polymerase digest RNA primer and replaces it with DNA
6) DNA ligase joins the discontinuous fragments of the lagging strand

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26
Q

Define DNA ligase

A

makes covalent bonds to join DNA strands; join Okazaki fragments and new segments in excision repair

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27
Q

Define RNA polymerase

A

copies RNA fromm a DNA template

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28
Q

Define primase

A

synthesize RNA primer

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29
Q

What direction is DNA replication in prokaryotes

A

bidirectional

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30
Q

Define DNA gyrase ( topoisomerase I) in prokaryote

A

release supercoiling

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31
Q

Define topoisomerase IV

A

seperate 2 loops

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32
Q

What are the 3 types of RNA

A

1) Ribosomal RNA ( rRNA)
2) Transfer RNA (tRNA)
3) Messenger RNA ( mRNA)

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33
Q

Define ribosomal rna

A

integral part of ribosomes

role in protein synthesis

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34
Q

Define transfer rna

A

transports amino acids during protein synthesis

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35
Q

Define messenger RNA

A

carries coded information from DNA to ribosomes

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36
Q

Describe transcription in prokayotes. What is needed and what direction does it go

A
  • synthesis of complementary mRNA strand
  • RNA polymerase
  • promoter
  • terminator
  • proceeds in 5 to 3 prime direction
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37
Q

Define translation

A

mRNA is translated into the language of proteins

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38
Q

Define codon. How many are there total? How many are sense and how many are nonsense?

A 
group of measured RNA that code for amino acid 
64 total codons
61 sense codons- 20 amino acids
1 start codon
3 nonsense codons
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39
Q

What is the start codon

A

AUG

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40
Q

What are the 3 stop codons

A

nonsense codon

UAA,UAG,UGA

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41
Q

Where does translation occur

A

ribosome

42
Q

What type of codon is tRNA considered

A

anticodon

43
Q

What are the 3 steps involved in translation

A

1) initiation
2) elongation
3) termination

44
Q

On the ribosome what are the 3 binding sites for tRNA

A

A site
P site
E site

45
Q

What are the 3 steps in transcription in eukaryptes

A

1) in the nucleus, a gene composed of exons and introns is transcribed to RNA by RNA polymerase
2) processing involved snRNPs in the nucleus to remove the intron-deprived RNA and splice together the exon-derived RNA into mRNA
3) After further modification, the mature mRNA travels to the cytoplasm where it directs proteins synthesis

46
Q

Define exon

A

code for proteins

47
Q

Define introns

A

do not code for proteins

48
Q

Define small nuclear ribonucleoproteins ( snRNPs)

A

splice exons together

49
Q

Define constitutive genes

A

expressed at a fixed rate
not under control
ex. enzymes involved in glycolysis

50
Q

Define inducible genes ( repressible genes)

A

control mechanism-induction and repression
regulates transcription of mRNA
these genes are only expressed as needed

51
Q

What is the the purpose of the operon model of gene expression

A

in bacteria it is a genetic regulatory system

set of operator,promoter, and structural genes

52
Q

What is the structure of operon

A

operon consists of the promoter and operator sites and structural genes that code for the protein

53
Q

Define promoter

A

segment of DNA where RNA polymerase initiates transcription of structural genes

54
Q

Define operator

A

segment of DNA that controls transcription of structural genes

55
Q

Define structural genes

A

regions of DNA that codes for the specific protein

56
Q

Define mutation

A

a permanent change in the base sequence of DNA

may be neutral, beneficial or harmful

57
Q

Define mutagens

A

a agent that cause mutations

can be anything physical/ chemical

58
Q

Define spontaneous mutations

A

occur in the absence of a mutagens

59
Q

What are the 2 types of mutations

A

point mutations

frameshift mutations

60
Q

Define point mutation

A

base substitution

change only one base pair

61
Q

What are the 3 sub types of point mutations

A

silent mutations
missense mutations
nonsense mutation

62
Q

Define silent mutations

A

normal protein

does not change amino acid sequence b/c many codes code for the same amino acid

63
Q

Define missense mutation

A

faulty proteins

amino acid is changed

64
Q

Define nonsense mutations

A 
incomplete protein
results in stop codon
stop codon ( UAA,UAG,UGA)
65
Q

Define frameshift mutation

A

insertion or deletion of one or more nucleotide pairs

shifts the translational “ reading frame”

66
Q

What are 2 types of mutagens

A

1) chemicals

2) radiation

67
Q

Describe chemical mutagens and 2 examples

A

nucleotide base analogs that replace nucleotides
resemble nucleotide
exp: bromouracil resembles thymine
aminopurine resembles adenine

68
Q

What chemicals react with DNA

A 
nitrous acid ( adenine to  bind to cytosine)
we can make antimicrobial agent
69
Q

What are the 2 types of radiation

A

1) Non-ionizing

2) ionizing

70
Q

Describe non-ionizing ( UV radiation)

A

pyrimidine dimers

71
Q

Describe ionizing ( xray, cosmic rays, gamma rays)

A

ionize water and produce free radicals

oxidize nucleotides and breaks sugar phosphate backbone

72
Q

What is the frequency of mutation

A

1 in 10 to the power of 9 replicated base pairs

mutagens increase rate to 1 in 10 to the 5th power

73
Q

What are the 3 ways of DNA repair

A

1) proofreading
2) mismatch repair
3) repair of thymine dimers

74
Q

Define proofreading as a form of dna repair

A

corrected by dna polymerase

reads newly added basepair

75
Q

Describe mistmatch repair as a form of dna repair

A

exonuclease
dna polymerase
ligase

76
Q

Describe repair of thymine dimers as a form of dna repair

A 
nucleotide excision repair ( dark repair)
direct repair ( ligth repair) visible light
77
Q

Define dark repair

A

DNA polymerase and ligase

78
Q

Define light repair

A

photolyase

activated by light

79
Q

Define genetic recombination

A

exchange of genes between 2 dna molecules

80
Q

Define crossing over of genetic material

A

2 chromospmes break and rejoin
insertion of foreign DNA into the chromosome
RecA protein: does the joining

81
Q

What 2 process does crossing over occur due to

A

1) vertical gene transfer

2) horizontal gene transfer

82
Q

Define vertical gene transfer

A

from organism to offspring

83
Q

Describe horizontal gene transfer

A

from cells to same generation

84
Q

What are the 3 types of horizontal genetic transfer in bacteria

A

1) transformation
2) conjugation
3) transduction

85
Q

Define transformation

A

genes transferred from 1 bacteria to another as “ naked” DNA

86
Q

What are the 3 steps in transformation

A

1) receipient cells take up donor DNA
2) donor DNA aligns with complementary bases
3) recombination occurs between donor dna and recipient dna

87
Q

Describe conjugation

A

plasmids transferred from 1 bacterium to another
special plasmid- F factor
F+ cells and F- cells

88
Q

What is required in conjugation

A

require cell to cell contact
gram negative-sex pili-projection from the donor’s cell surface
gram positive- sticky surface molecules

89
Q

Why does antibiotic resistence occur

A

becuase of conjugation

b/c plasmid can only be transferred by conjugation

90
Q

Describe transduction

A

DNA is transferred from a donor cell to a recipient cell via bacteriophage
bacteriophage or phage-virus that infects bacteria

91
Q

What are the 2 types of transduction

A

1) Generalized transduction

2) specialized transduction

92
Q

Define generalized transduction

A

random DNA packaged inside the phage and transferred

93
Q

Define specialized transduction

A

specific bacterial genes are packaged inside the phage and transferred
ex. toxins

94
Q

What are the 5 steps of transduction

A

1) a phage infects the donor bacterial cell
2) phage DNA and proteins are made and the bacterial chromosomes is broken into pieces
3) occasionally during phage assembly,pieces of bacterial DNA are packaged in a phage capsid. then the donor cell lyse and release phage particle containing bacterial dna
4) a phage carrying bacterial DNA infects a new host cell, the recipient cell
5) recombination can occur,producing a recombinant cell with a genotype different from both the donor and recipient cells

95
Q

Describe plasmids

A

self-replicating circular pieces of DNA
often code for proteins that enhances the pathogenicity of a bacterium
1-5% the size of a bacterial chromosome

96
Q

What are the 2 types of plasmids

A

1) conjugative plasmids

2) dissimilation plasmids

97
Q

Define conjugative plasmids

A

carries genes for sex pili and transfer of the plasmids

98
Q

Define dissimilation plasmids

A

encode enzymes for the catabolism of unusal compounds

99
Q

Define resistance factors (R factors)

A

encode antibiotic resistance
ex. mercury resistance,sulfonamide resistance,streptomycine resistance
chlormphenicol resistance, tetracycline resistance

100
Q

Define transposons

A

small segments of DNA ( chromosome of plasmids)
can move from one region of DNA to other
contain insertion sequence (IS) code for transposases
complex transposons carry other genes ( antibiotic resistance genes, toxin production genes)

101
Q

Define transposases

A

cuts and reseals DNA

Microbiology (16 decks)

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