ch 9: microbial genetics - dewhozitz.netdewhozitz.net/micrv01/9-micgenetics96.pdf · ch 9:...
TRANSCRIPT
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Ch 9: Microbial Genetics
Some videos: http://highered.mcgraw-hill.com/sites/0073375292/student_view0/chapter9/
animations.htm (see also YouTube, etc.)
(2.23-4)
DNA Base-pairs
antiparallel
5’
5’ 3’
3’
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Eukaryotic chromosomes (condensation for cell division)
Gene Genotype Phenotype
Serratia at 25 oC & 37 oC
Agar Broth
DNA replication:
Semi-conservative
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DNA replication:
Replication fork
http://www.youtube.com/watch?v=teV62zrm2P0 3’
Replication of a prokaryotic chromosome
Replication of a eukaryotic chromosome
Where the energy for synthesis comes from?
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DNA can be methylated (-CH3) to control of gene expression to help with DNA replication initiation to help with DNA repair protection against viral infection
Example:
Transcription 3 kinds of RNA for protein translation
Transcription
http://www.dnalc.org/resources/3d/12-transcription-basic.html
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Transcription: Prokaryotic vs. Eukaryotic
place
Transcription: Prokaryotic vs. Eukaryotic
mechanisms
structures
cap tail
Translation: Universal Genetic Code
41 or 42 or 43 codons?
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ribosomes
tRNAs
Where it binds to mRNA
more 3D view
Flattened (2D) view
Translation: initiation
exit
Peptidyl Amino-acyl
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Translation: elongation
Translation: termination
http://www.dnalc.org/resources/3d/15-translation-basic.html
Negative control of gene expression: prokaryotic genes in operons Example: lac operon - makes enzymes for lactose catabolism
inducible
Jacob & Monod
more usual
more unusual
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Additional control on the lac operon: positive control (the presence of lactose is insufficient) also need CAP (= catabolic activator protein) on promoter
[glucose] high -> [cAMP] low [glucose] low -> [cAMP] high
Negative control of gene expression: prokaryotic genes in operons
Example: arg operon: makes enzymes for arginine synthesis
Repressible
(Note: most textbooks & videos use trp operon instead; works same way as this one.)
more usual
more unusual
Regulatory RNAs riboswitches
(from Wikipedia)
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1 kind of DNA repair: excision repair
Positive selection
Negative selection with replica plating
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Ames Test for mutagens
Vertical transfer = between generations {from parent(s) to offspring}
Horizontal transfer = between contemporaries (sometimes different species) Eg: How the jellyfish got its sting (from a bacterium)
Published 28 September 2008 | Nature
Usual genetic recombination mechanisms in eukaryotes
independent assortment & crossing-over during meiosis
sex
Transformation: get DNA from the environment (Griffith)
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Bacterial conjugation =
get DNA from another living bacterium
Transduction: get DNA from a virus
(Discuss Section 9.6 with lectures on viruses)
Transposons aka. “jumping genes”
B. McClintock (NP 1983)
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http://www.dnalc.org/resources/3d/index.html 3-D animation listed by name: DNA Molecule: Basepairing Chargaff's Ratios Chromosome 11 Flyover Chromosome Map DNA Has Four Units DNA Unzip How DNA is Packaged (Basic) How DNA is Packaged (Advanced) How Much DNA Codes for Protein? Triple Helix Transcription & Translation: The Central Dogma of Biology Transcription (Basic) Transcription (Advanced) Triplet Code RNA splicing mRNA splicing Translation (Basic) Translation (Advanced)
Replication: Mechanism of Replication (Basic) Mechanism of Replication (Advanced) Replicating the Helix Experiments & Techniques: Mechanism of Recombination Microarray Polymerase Chain Reaction Private Project Sequencing Public Project Sequencing Sanger Sequencing Disease & Mutation: Cell Signals DNA Damage How Gleevec® Works Pathways to Cancer Sickle Cell Tumor Growth