Download Microbial Genetics

Microbial Genetics
The how and why of information flow in
living things.
What exactly is living?
Genetics Terms
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Genome:
Chromosome
Gene
Base pair
Genetic code
Genotype
Phenotype
The Polymers of life
• Define Polymer
• Define Monomer
• What are the polymers of life?
• Why use polymers?
Determine Relatedness
Clinical Focus, p. 223
Determine Relatedness
• Which strain is
more closely
related to the
Uganda strain?
Strain
% Similar to
Uganda
Kenya
71%
U.S.
51%
The genetic Code
• Name the monomers that make up the
genetic code.
• Name the monomers that make up
Proteins
What is the flow of genetic
information in the bacterial cell?
Verb
Enzyme
Substrate
Product
Genetic Map of the
Chromosome of E. coli
Figure 8.1b
The Flow of Genetic Information
Figure 8.2
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.
Semiconservative Replication
Figure 8.3a
DNA Synthesis
Figure 8.4
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
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
Transcription
Figure 8.7
The Process of Transcription
Figure 8.7
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.
Degenerate: Most amino acids are
code for by more than one codon.
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64 codons
3 are nonsense
Start codon Aug is for methionine.
See the codon sequence.
The Genetic Code
Figure 8.8
Simultaneous Transcription &
Translation
Figure 8.10
The Process of Translation
Figure 8.9
The Process of Translation
Figure 8.9
The Process of Translation
Figure 8.9
The Process of Translation
Figure 8.9
The Process of Translation
Figure 8.9
The Process of Translation
Figure 8.9
The Process of Translation
Figure 8.9
The Process of Translation
Figure 8.9
Info
• From information storage to reality.
• What determines what info is used
• What determines how information is
moved about.
Regulation
• Constitutive genes are expressed at a
fixed rate
• Other genes are expressed only as needed
– Repressible genes
– Inducible genes
– Catabolite repression
Operon
ANIMATION Operons: Overview
Figure 8.12
Induction
Figure 8.12
Induction
Figure 8.12
Repression
Figure 8.13
Repression
ANIMATION Operons: Induction
ANIMATION Operons: Repression
Figure 8.13
Catabolite Repression
(a) Growth on glucose or lactose alone
(b) Growth on glucose and lactose
combined
Figure 8.14
• Lactose present,
no glucose
• Lactose + glucose
present
Figure 8.15
Types of Bacterial sex
Name
Process
What it is
Comments
Genetic Recombination
• The rearrangement of genes.
• Crossing over is where genes are
recombined within a chromosome.
Transformation
• Naked DNA is transferred from one
bacteria to another.
• Was the first experiment that showed DNA
was the genetic information
Genetic Recombination
Figure 8.25
Genetic Transformation
ANIMATION Transformation
Figure 8.24
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.
Bacterial Conjugation
Figure 8.26
Conjugation in E. coli
Figure 8.27a
Conjugation in E. coli
Figure 8.27b
Conjugation in E. coli
Figure 8.27c
Transduction
• DNA is passed from one bacterium to
another in a bacteriophage and put into
recipients DNA.
Transduction by a Bacteriophage
Figure 8.28
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?
Control of gene expression
• Repression
• Induction
The Operon Model of gene
expression
• Repression:
regulatory mechanism
inhibits gene
expression
• Induction: a process
that turn on gene
expression
Repressible Operon
Inducible operon
Where are the points of control
If a cell has all the genes that
are needed then why are they
not expressed at one time?
Mutations
• What are they?
Mutations
• What can they do
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
Mutation
• Base substitution
(point mutation)
• Missense
mutation
• Change in one
base
• Result in change in
amino acid
Figure 8.17a, b
Mutation
• Nonsense mutation • Results in a
nonsense codon
Figure 8.17a, c
Mutation
• Frameshift mutation • Insertion or deletion
of one or more
nucleotide pairs
Figure 8.17a, d
The Frequency of Mutation
Chemical Mutagens
Figure 8.19a
Radiation
• Ionizing radiation (X rays and gamma
rays) causes the formation of ions that can
react with nucleotides and the deoxyribosephosphate backbone
Radiation
• UV radiation
causes thymine
dimers
Figure 8.20
Repair
• Photolyases separate thymine dimers
• Nucleotide excision repair
Figure 8.20
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
Replica Plating
Figure 8.21
Ames Test for Chemical
Carcinogens
Figure 8.22
The old and new genetics
• Screening and selection of mutants
What do you think we would call
the new genetics?