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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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(RNA 2.23)

Theory

Idea

Prokaryotic chromosome(s)

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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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Mutations

silent

Mutagenic radiation

UV

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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