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Chapter 8: Microbial Genetics

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Title: Chapter 8: Microbial Genetics


1
Chapter 8 Microbial Genetics
2
  • Genome genetic information in a cell
  • Chromosome contains the genes-segments of DNA
  • DNA nucleotide base pairs - genetic code for
    proteins
  • Central Dogma
  • DNA - RNA - Proteins
  • Genomics sequencing and molecular
    characterization of genomes

Bacteria Single circular chromosome Looped and
folded and attached at one or several points to
the plasma membrane
3
THAT SPELLS DNA
  • Jonathan Coulton

http//www.jonathancoulton.com/store/downloads/
4
  • We start the story when Mom met Dad
  • And they danced all night and he took her home
  • It might have been all the wine they had
  • But they rolled the dice and won your genome
  • Then you grew and you grew and one day you were
    you
  • And you looked like your father and mother
  • IF youre looking for someone convenient to blame
  • You can take your pick its one or the other
  • DNA, youre in my heart
  • DNA, in fact youre in every part of my body
  • Each cell has a nucleus, each nucleus has
    chromosomes
  • And DNA, baby, that spells DNA

5
  • Guanine met Cytosine, fell in love
  • And then Thymine got busy with Adenine
  • They sent the messenger-RNA
  • To the ribosome to make more protein
  • And while its killing you dead it will mess with
    your head
  • And its the light in the dark that will guide
    you
  • Its the pages and pages of what you are like
  • In the giant book thats hidden inside you
  • DNA, youre in my heart
  • DNA, in fact youre in every part of my body
  • Each cell has a nucleus, each nucleus has
    chromosomes
  • And DNA, baby, that spells DNA

6
  • If it says TGGTCGAAC
  • Then you might get the cancer
  • If it says GTCACGACAGG
  • Then you shouldnt eat shrimp or nuts
  • If it says TATACACATATCCTCGT
  • Then youll probably wish that you didnt know
  • The time will come when youre almost gone
  • And you try to guess but youll never know
  • You do your best and you soldier on
  • Every day youre here till its time to go
  • All the good things and bad that you do or dont
    have
  • You can find out for sure if you gotem
  • But theres a spiraling staircase that youre
    falling down
  • And youre nothing but dead at the bottom

7
  • DNA, youre in my heart
  • DNA, in fact youre in every part of my body
  • Each cell has a nucleus, each nucleus has
    chromosomes
  • And DNA, baby, that spells DNA

8
DNA RNA PROTEINS
Replication Transcription
Translation
9
DNA RNA PROTEINS
Replication Transcription
Translation
  • Semiconservative replication each new DNA
    molecule contains one original and one new strand
  • Requires TONS of energy - supplied by the
    nucleotides (nucleoside triphosphates)
  • Two phosphates are removed to add the
    nucleotide to a
  • growing stand
  • Hydrolysis (exergonic)
  • Accurate mistakes made in 1 in every 1010
    bases Proofreading-DNA pol

10
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11
DNA RNA PROTEINS
Replication Transcription
Translation
  • Bacteria
  • Some replicate bidirectionally around the
    chromosome
  • Two replication forks move in opposite direction
    away from the origin of replication
  • Eventually meet when replication is complete
  • Ex E.coli

12
file///Volumes/Tortora_Micro_10e_DVD1/Chapter_08/
C_Animations_and_Videos/a_Microbiology_Animations/
dna_replication.swf
13
TRANSCRIPTION
  • file///Volumes/Tortora_Micro_10e_DVD1/Chapter_08/
    C_Animations_and_Videos/a_Microbiology_Animations/
    transcription_process.swf

14
TRANSLATION

15
file///Volumes/Tortora_Micro_10e_DVD1/Chapter_08/
C_Animations_and_Videos/a_Microbiology_Animations/
translation_process.swf file///Volumes/Tortora_Mi
cro_10e_DVD1/Chapter_08/C_Animations_and_Videos/a_
Microbiology_Animations/translation.swf
16
GENE REGULATION
  • Turning on and off genes
  • Save energy and resources
  • Repression Turns OFF
  • Response to overabundance of an end product
  • Repressors block RNA pol

17
GENE REGULATION
  • Induction Turns ON
  • Inducer acts to induce transcription
  • EX lac operon
  • E. coli (bacteria that live in intestines of
    mammals)
  • Discovered how genes control the metabolism of
    the sugar lactose
  • Lactose disaccharide made of glucose and
    galactose
  • Milk sugar
  • http//www.youtube.com/watch?voBwtxdI1zvkfeature
    related

18
When there is/is not lactose
  • LACTOSE PRESENT It induces E. coli to produce
    three enzymes which will metabolize lactose
  • LACTOSE ABSENT three enzymes will not be made.
    Lactose will not be broken down.

19
DNA of E.coli
  • Regulator gene codes for repressor gene
  • Promoter DNA segment that is recognized by the
    enzyme RNA pol
  • Operator DNA segment that serves as a switch
    controlling the access of RNA pol to the promoter
  • Structural genes code for 3 enzymes that break
    down lactose

20
Operon turned off
  • Repressor protein attaches to the operator
    physically blocking RNA pol from attaching

RNA pol
21
Operon turned on
  • Lactose present (acts as inducer starts gene
    expression)
  • Binds to the repressor protein
  • Repressor changes shapes and detaches from
    operator
  • RNA pol is not blocked anymore
  • All three enzymes can be produced

22
Operator turned on
lactose
23
Why is this good?
  • E. coli is able to turn off and on genes when
    lactose is present/absent
  • Bacteria saves resources and produce only those
    proteins that are needed

24
Lets watch it again
  • http//www.youtube.com/watch?voBwtxdI1zvkfeature
    related

25
MuTaTiOnS
26
  • GOOD
  • New enhanced activity that benefits the cell
  • BAD
  • Inactive or less active, lethal?
  • SILENT(neutral)
  • No change in activity

27
Types of Mutations
  • Base Substitution (point)
  • Single base in DNA is replaced
  • Missense mutation substitution results in an
    amino acid substitution
  • Nonsense mutation creates a stop codon in the
    middle of mRNA....preventing synthesis of protein

28
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29
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30
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31
Types of Mutations
  • Frameshift
  • One or a few nucleotide pairs are deleted or
    inserted in the DNA
  • Change the reading frame of codons
  • Mutations can occur spontaneously or by
    mutagens

32
(No Transcript)
33
(No Transcript)
34
MUTAGENS
  • Chemical
  • Nitrous acid (HNO2) causes A to bond with C
    instead of T

35
MUTAGENS
  • Radiation x-rays, UV rays, gamma rays
  • Cause electrons to pop out of their usual shells
  • Ions can combine with bases in DNA, resulting in
    errors in DNA
  • Breakage of covalent bonds in sugar-phosphate
    backbone-breaks in chromosomes

36
  • Exposure to UV causes Ts to cross link forming a
    thymine dimer
  • Unless repaired, these may cause serious damage
    or death to the cells because it cannot properly
    transcibe or replicate.
  • Some organisms have enzymes that can repair these
    dimers

37
Genetic Transfer and Recombination
  1. Conjugation transfer of a plasmid
  2. Transduction transfer of DNA via a virus
  3. Transformation genes transferred from one
    bacterium to another as naked DNA

38
Conjugation
  • Movement of a plasmid
  • b/w two cells
  • Plasmid small, self-replicating, gene-containing
    circular piece of DNA
  • Requires direct cell to cell contact
  • Opposite mating types (donor cell has a plasmid,
    recipient cells do not)

file///Volumes/Tortora_Micro_10e_DVD1/Chapter_08/
C_Animations_and_Videos/a_Microbiology_Animations/
conjugation.swf
39
(No Transcript)
40
Transduction
  • Bacterial DNA is transferred from a donor cell to
    recipient inside a virus that infects bacteria
  • Bacteriophage (phage)

41
TRANSFORMATION
  • First done 70 yrs ago Griffith
  • http//www.dnatube.com/video/997/Transformation

42
HOW DOES THIS HAPPEN?
  • Can happen naturally after cell death and cell
    lysis
  • Cell wall becomes permeable to large DNA
    molecules
  • Use surface proteins and type 4 pili to extend
    and take it in
  • Works best when donor and recipient cells are
    closely related
  • Artificial transformation
  • Competence when recipient cell is in a
    physiological state to take up donor DNA
  • Changing the ionic strength of the medium and
    heating the cells in the presence of positive
    ions (Calcium)
  • Makes cell membrane permeable

43
We are going to do this!!!
44
pBLU Transformation
  • Use an ampicillin-sensitive strain of E. coli,
    incapable of producing b-galactosidase for
    lactose breakdown
  • Induce it to take up pBLU plasmid DNA
  • Plasmid contains genes for Ampicillin resistance
    and the entire b-glactosidase gene

45
  • http//www.biologie.uni-hamburg.de/b-online/librar
    y/onlinebio/14_1.jpg
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