Title: Chapter 8: Microbial Genetics
1Chapter 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
3THAT SPELLS DNA
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
8DNA RNA PROTEINS
Replication Transcription
Translation
9DNA 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(No Transcript)
11DNA 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
12file///Volumes/Tortora_Micro_10e_DVD1/Chapter_08/
C_Animations_and_Videos/a_Microbiology_Animations/
dna_replication.swf
13TRANSCRIPTION
- file///Volumes/Tortora_Micro_10e_DVD1/Chapter_08/
C_Animations_and_Videos/a_Microbiology_Animations/
transcription_process.swf
14TRANSLATION
15file///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
16GENE REGULATION
- Turning on and off genes
- Save energy and resources
- Repression Turns OFF
- Response to overabundance of an end product
- Repressors block RNA pol
17GENE 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
18When 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.
19DNA 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
20Operon turned off
- Repressor protein attaches to the operator
physically blocking RNA pol from attaching
RNA pol
21Operon 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
22Operator turned on
lactose
23Why 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
24Lets watch it again
- http//www.youtube.com/watch?voBwtxdI1zvkfeature
related
25MuTaTiOnS
26- GOOD
- New enhanced activity that benefits the cell
- BAD
- Inactive or less active, lethal?
- SILENT(neutral)
- No change in activity
27Types 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(No Transcript)
29(No Transcript)
30(No Transcript)
31Types 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)
34MUTAGENS
- Chemical
- Nitrous acid (HNO2) causes A to bond with C
instead of T
35MUTAGENS
- 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
37Genetic Transfer and Recombination
- Conjugation transfer of a plasmid
- Transduction transfer of DNA via a virus
- Transformation genes transferred from one
bacterium to another as naked DNA
38Conjugation
- 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)
40Transduction
- Bacterial DNA is transferred from a donor cell to
recipient inside a virus that infects bacteria - Bacteriophage (phage)
41TRANSFORMATION
- First done 70 yrs ago Griffith
- http//www.dnatube.com/video/997/Transformation
42HOW 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
43We are going to do this!!!
44pBLU 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