Microbial Genetics

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Microbial Genetics

• The how and why of information flow in living
  things.
• What exactly is living?

2
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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Determine Relatedness
Clinical Focus, p. 223
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Determine Relatedness

• Which strain is more closely related to the
  Uganda strain?

Strain Similar to Uganda
Kenya 71
U.S. 51
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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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Genetic Map of the Chromosome of E. coli
Figure 8.1b
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The Flow of Genetic Information
Figure 8.2
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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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Semiconservative Replication
Figure 8.3a
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DNA Synthesis
Figure 8.4
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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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Transcription
Figure 8.7
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The Process of Transcription
Figure 8.7
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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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The Genetic Code
Figure 8.8
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Simultaneous Transcription Translation
Figure 8.10
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The Process of Translation
Figure 8.9
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The Process of Translation
Figure 8.9
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The Process of Translation
Figure 8.9
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The Process of Translation
Figure 8.9
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The Process of Translation
Figure 8.9
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The Process of Translation
Figure 8.9
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The Process of Translation
Figure 8.9
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The Process of Translation
Figure 8.9
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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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Operon
ANIMATION Operons Overview
Figure 8.12
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Induction
Figure 8.12
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Induction
Figure 8.12
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Repression
Figure 8.13
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Repression
ANIMATION Operons Induction
ANIMATION Operons Repression
Figure 8.13
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Catabolite Repression
Figure 8.14
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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.

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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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Genetic Recombination
Figure 8.25
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Genetic Transformation
ANIMATION Transformation
Figure 8.24
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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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Bacterial Conjugation
Figure 8.26
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Conjugation in E. coli
Figure 8.27a
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Conjugation in E. coli
Figure 8.27b
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Conjugation in E. coli
Figure 8.27c
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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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Transduction by a Bacteriophage
Figure 8.28
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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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Mutation

• Base substitution (point mutation)
• Missense mutation

• Change in one base
• Result in change in amino acid

Figure 8.17a, b
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Mutation

• Nonsense 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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Chemical Mutagens
Figure 8.19a
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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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Radiation

• UV radiation causes thymine dimers

Figure 8.20
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Repair

• Photolyases separate thymine dimers
• Nucleotide excision repair

Figure 8.20
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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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Replica Plating
Figure 8.21
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Ames Test for Chemical Carcinogens
Figure 8.22
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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?