ch 8
TRANSCRIPT
![Page 1: Ch 8](https://reader036.vdocuments.site/reader036/viewer/2022081421/556c70d9d8b42ad85e8b5077/html5/thumbnails/1.jpg)
Microbial Genetics
The how and why of information flow in living things.
What exactly is living?
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Genetics Terms
• Genome:
• Chromosome
• Gene
• Base pair
• Genetic code
• Genotype
• Phenotype
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The Polymers of life
• Define Polymer
• Define Monomer
• What are the polymers of life?
• Why use polymers?
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Clinical Focus, p. 223
Determine Relatedness
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Determine Relatedness
Strain % Similar to Uganda
Kenya 71%
U.S. 51%
• Which strain is more closely related to the Uganda strain?
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The genetic Code
• Name the monomers that make up the genetic code.
• Name the monomers that make up Proteins
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What is the flow of genetic information in the bacterial cell?
Verb Enzyme Substrate Product
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Figure 8.1b
Genetic Map of the Chromosome of E. coli
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Figure 8.2
The Flow of Genetic Information
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DNA Replication
• The double strand of DNA is separated.
• DNA polymerase reads the DNA strand and creates another.
• The newly synthesized DNA contains an old strand and a new strand.
• The two new strands are then separated into the two new daughter cells.
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Figure 8.3a
Semiconservative Replication
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Figure 8.4
DNA Synthesis
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DNA Synthesis
• DNA is copied by DNA polymerase– In the 5' 3' direction– Initiated by an RNA primer– Leading strand is synthesized continuously– Lagging strand is synthesized discontinuously – Okazaki fragments – RNA primers are removed and Okazaki
fragments joined by a DNA polymerase and DNA ligase
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Transcription
• A sequence of DNA is relaxed and opened up.
• RNA polymerase synthesizes a strand of RNA
• RNA uses ACGU
• Starting point is a promoter
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Figure 8.7
Transcription
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Figure 8.7
The Process of Transcription
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Translation
• mRNA associates with ribosome's (rRNA and protein)
• 3-base segments of mRNA specify amino acids and are called codons.
• Genetic code: relationship among nucleotide sequence and corresponding DNA sequence.
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Degenerate: Most amino acids are code for by more than one codon.
• 64 codons
• 3 are nonsense
• Start codon Aug is for methionine.
• See the codon sequence.
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Figure 8.8
The Genetic Code
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Figure 8.10
Simultaneous Transcription & Translation
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Figure 8.9
The Process of Translation
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Figure 8.9
The Process of Translation
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Figure 8.9
The Process of Translation
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Figure 8.9
The Process of Translation
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Figure 8.9
The Process of Translation
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Figure 8.9
The Process of Translation
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Figure 8.9
The Process of Translation
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Figure 8.9
The Process of Translation
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Info
• From information storage to reality.
• What determines what info is used
• What determines how information is moved about.
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Regulation
• Constitutive genes are expressed at a fixed rate
• Other genes are expressed only as needed– Repressible genes– Inducible genes– Catabolite repression
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Figure 8.12
ANIMATION Operons: Overview
Operon
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Figure 8.12
Induction
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Figure 8.12
Induction
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Figure 8.13
Repression
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Figure 8.13
ANIMATION Operons: Induction
ANIMATION Operons: Repression
Repression
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Figure 8.14
(a) Growth on glucose or lactose alone (b) Growth on glucose and lactose combined
Catabolite Repression
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• Lactose present, no glucose
• Lactose + glucose present
Figure 8.15
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Types of Bacterial sex
Name Process What it is Comments
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Genetic Recombination
• The rearrangement of genes.
• Crossing over is where genes are recombined within a chromosome.
![Page 40: Ch 8](https://reader036.vdocuments.site/reader036/viewer/2022081421/556c70d9d8b42ad85e8b5077/html5/thumbnails/40.jpg)
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Transformation
• Naked DNA is transferred from one bacteria to another.
• Was the first experiment that showed DNA was the genetic information
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Figure 8.25
Genetic Recombination
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Figure 8.24
ANIMATION Transformation
Genetic Transformation
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Conjugation
• DNA transferred from one bacteria to another by a sex pillus.
• Information of transfer coded by a plasmid called F+
• Hfr cells occur when F+ plasmid goes into the host chromosome and recombines, it will then draw across the DNA.
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Figure 8.26
Bacterial Conjugation
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Figure 8.27a
Conjugation in E. coli
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Figure 8.27b
Conjugation in E. coli
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Figure 8.27c
Conjugation in E. coli
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Transduction
• DNA is passed from one bacterium to another in a bacteriophage and put into recipients DNA.
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Figure 8.28
Transduction by a Bacteriophage
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Alternate forms of the chromosome format.
• Plasmids: self replicating circular molecules of NDA
• Transposes: small segments of DNA that can move into different parts of the genome.
• Can these have an effect on Evolution?
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Control of gene expression
• Repression
• Induction
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The Operon Model of gene expression
• Repression: regulatory mechanism inhibits gene expression
• Induction: a process that turn on gene expression
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Repressible Operon
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Inducible operon
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Where are the points of control
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If a cell has all the genes that are needed then why are they
not expressed at one time?
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Mutations
• What are they?
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Mutations
• What can they do
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Mutation
• A change in the genetic material
• Mutations may be neutral, beneficial, or harmful
• Mutagen: Agent that causes mutations
• Spontaneous mutations: Occur in the absence of a mutagen
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• Base substitution (point mutation)
• Missense mutation
Mutation
• Change in one base
• Result in change in amino acid
Figure 8.17a, b
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• Nonsense mutation
Mutation
• Results in a nonsense codon
Figure 8.17a, c
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Mutation
• Frameshift mutation• Insertion or deletion of one or more nucleotide pairs
Figure 8.17a, d
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The Frequency of Mutation
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Figure 8.19a
Chemical Mutagens
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Radiation
• Ionizing radiation (X rays and gamma rays) causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone
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Figure 8.20
Radiation
• UV radiation causes thymine dimers
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Figure 8.20
Repair• Photolyases separate thymine dimers
• Nucleotide excision repair
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Selection
• Positive (direct) selection detects mutant cells because they grow or appear different
• Negative (indirect) selection detects mutant cells because they do not grow– Replica plating
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Figure 8.21
Replica Plating
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Figure 8.22
Ames Test for Chemical Carcinogens
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The old and new genetics
• Screening and selection of mutants
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What do you think we would call the new genetics?