Transcript Genetics of Viruses and Bacteria

Genetics of Viruses and
Bacteria
Ch 19 & 20
Everything
you need
to know
about
viruses.
Infected? With What?
How can you tell?
• Start with Symptoms: illness is abrupt and is
characterized by fever, headache, joint and
muscle aches, sore throat, and weakness,
followed by diarrhea, vomiting, and stomach
pain. A rash, red eyes, internal and external
bleeding from all orifices.
• Who is at risk? Persons on the southeast coast
of Africa, Congo,Sudan, Zaire, and Uganda
• Treatment: No known treatment
• Disease: Ebola Hemorragic Fever
• Surveillance: CDC SPECIAL PATOGENS UNIT,
WHO
Ebola
Outbreak
history
Infected? With What?
How can you tell?
How the flu
Changes.
• Start with Symptoms: Myalgia, fever,
headache, extreme tiredness, dry cough,
sore throat, runny or stuffy nose, and
muscle aches.
• Who is at risk? Everyone
Antigenic
Shifts
• Treatment: Bed Rest and Fluids
• Disease: Influenza
• Surveillance: CDC and WHO
Avian Flu
PBS
The Bacteriophage
or Phage
• Viruses that attack bacteria
Viruses: Are They Alive?
Characteristics of
Viruses
• Much smaller than a bacterium.
• Have 2 essential structural
features: Nucleic Acid (DNA or
RNA) and Protein Coat called a
capsid surrounding it.
• Must have a host (host range)
in order to propagate itself.
Viral Shapes Fig 19.3
Grouping Viruses
Fig 19.1
• Presence of a Capsid and
Envelope
• Whether they contain RNA or
DNA
• Shape
Virus Reproduction
• DNA viruses can immediately
produce RNA to construct new
viruses or become part of
host’s DNA.
• RNA viruses must uses reverse
transcriptase.
Hiv
Replication
HIV is a retrovirus: uses reverse
transcriptase.
Provirus: integrated
viral DNA
Phage Lysogenic Cycle Details
Fig 19.6
• Virus replicates without destoying the host
cell.
– Prophage: Dormant virus within host (HIV)
– Prophage switches to lytic phase.
– Temperate viruses are capable of both lytic
and lysogenic cylces within a bacterium.
The Lysogenic
Cycle
The Lysogenic
Cycle
Phage Lytic cycle details.
• DNA replication produces more viral DNA
• Transcription and translation produce
protein coats and glycoprotein spikes
The Lytic
Cycle
Virus Evolution
• Plasmids (circular DNA in bacteria and
Yeast), or Transposons (mobile DNA
segments) may have escaped.
• May have originated when fragments of
host genes escaped or were expelled
from cells or from prions.
• Can mutate quickly.
• Treated with antivirals
• Prevented by vaccines.
Other non-life forms
Viroids and Prions
• Viroids: the smallest particles
that are able to replicate.
• A short, circular RNA that has
no capsid
• They disrupt plant cell
metabolism
• Prions: (PREE-ahnz) are misfolded
proteins that clump together inside a
cell. Normal proteins begin to fold and
clump as well. The clumping kills the
cell. Fig. 19.11
• Composed of about 250 amino acids
and have no associated nucleic acid.
• Indestructible. Can’t destroy or
deactivate through normal cooking
temperatures.
• Prions cause scrapie in sheep,
mad cows disease, and
Creutzfeld-Jakob disease in
humans
Good review
Clips
Of General
Concepts
Infected? With What?
How can you tell?
• Start with Symptoms: Severe abdominal
pain, weight loss, stomach ulcers, nausea
and vomiting.
• Who is at risk? Everyone
• Treatment: Antibiotics
• Disease: Stomach Ulcers caused by H.
Pylori
• Surveillance: Both National and
International By CDC and WHO
How it
Works
What are bacteria?
• Single celled microscopic
prokaryotes
• Circular DNA condensed into a
nuceoid. (no nuclear membrane)
• With or without a peptidoglycan in
cell wall.
• Autotrophs or heterotrophs
How are bacteria named?
Group Arrangement:
Strepto=
Shape:
Chains
Staphylo=
Clusters
Domain Bacteria:
live in moderate
environments. Characteristics:
Bacteria on
Contact lens
• Unicellular
• Prokaryotes
• No introns
• E.Coli (used in genetic
engenering to make insulin)
Plaque on teeth
• Peptidoglycan cell
walls
• Anaerobes or Aerobes
• Some are Decomposers
or Pathogens
• Some use conjugation
• No organelles or nucleus
• Some used to fix
nitrogen for the nitrogen
cycle
• Viruses placed here for
lack of a place to put
them.
What is the bacterial cell wall made
of?
• Peptidoglycan (polypeptides and sugar)
– Gram Positive: thick peptidoglycan
Mycobacterium leprae or
• Stains Purple
Leprosy
• Penicillin puts holes in the peptioglycan
– Gram Negative: thin peptidoglygan and
lipopolysaccharides coating cell wall.
• Stains Red (When she felt negative she saw red)
• More antibiotic resistant.
• Lipids are toxic to humans
E. Coli
Parts of a bacteria.
• All have a Cell Wall and Plasma
Membrane
• Cytoplasm, Pilli, Plasmid
• Some have Flagella and Capsules
• May make Endospores when
Bacterial
Conjugation
dormant for protection.
Don’t Look!
Conjugation:
primitive sexual method.
Bacterial transformation.
Discovered by Frederick
Griffith 1927.
Donating DNA
How do bacteria reproduce?
• Binary Fission = asexual.
• Replicate their DNA in Both directions
from a single point of origin= Theta
Replication, because it looks like Θ.
• Very few mutations. But reproduce
often.
What is a plasmids and what do
they do?
• Plasmid: foreign, circular, self-replicating
DNA molecule in a bacterium.
• Bacterium may have more than one
plasmid.
• Express genes they carry
– Create pilli = F plasmid
– Resist antibiotics = R plasmid
What is an Operon?
• A set of genes found in bacteria and phages that
combined with the promoter and operator
express those genes.
• A gene regulation mechanism.
• Jacob and Monod (1940) discovered the first
operon in E.coli. They found 2 types:
– Lac operon: Inducible operon. Always off
– Tryptophan operon: Repressible operon. Always on.
– The correct signal will switch the Lac on or the
Tryptophan off.
Operon Operations
Lac Operon Overview
• Terms to know:
• Promoter: Region of the DNA RNA
polymerase binds to
• Repressor: binds to operator preventing
RNA polymerases attachment.
Noncompetitive inhibition.
• Operator: Site for repressor attachment at
the start of the bacterial operon.
The AP Version of the Lac Operon
The Lac operon: Inducible
• Job of the Lac operon: to utilize lactose turning it
into glucose and glactose.
• Three enzymes necessary to do this:
• B-galactosidase, permease, and transacetylase
• RNA polymerase must bind to the promoter to
allow the cell to utilize lactose.
– Allosteric effector, allolactose, acts as an inducer.
Allolactose binds to the repressor causing a
conformation of the repressor. It can not longer
repress.
• If a repressor binds to the operator
(noncompetitive inhibition) lactose can not be
utilized.
Tryptophan Operon: Repressible
• Continuously on unless switched off by a
corepressor.
• rRNA polymerase binds to the promoter and
transcribes.
• Repressor combines with the corepressor on
the tryptophan gene it changes conformation,
binds to the operator = RNA polymerase can
not bind and transcription is blocked.
• Turned of when tryptophan levels are high,
negative feedback.
Tryptophan Operon
What is an Allosteric effector?
• Tryptophan: Tryptophan Operon
• Lactose: Lac Operon
• The binding of a regulatory molecule to a
protein at one site that affects the function
of the protein at a different site.
AP Bio Tryp