genetics of viruses and bacteria ch 19 & 20 everything you need to know about viruses
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Genetics of Viruses and BacteriaCh 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 EbolaOutbreakhistory
Infected? With What?How can you tell?• Start with Symptoms: Myalgia, fever,
headache, extreme tiredness, dry cough, sore throat, runny or stuffy nose, and muscle aches.
• Who is at risk? Everyone
• Treatment: Bed Rest and Fluids
• Disease: Influenza
• Surveillance: CDC and WHO
How the fluChanges.
Avian FluPBS
AntigenicShifts
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.
Grouping VirusesFig 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
Phage Lysogenic Cycle DetailsFig 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 LysogenicCycle
Phage Lytic cycle details.
• DNA replication produces more viral DNA
• Transcription and translation produce protein coats and glycoprotein spikes
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 reviewClips
Of GeneralConcepts
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
Domain Bacteria: live in moderate environments. Characteristics:
• Unicellular• Prokaryotes• No introns
• Peptidoglycan cell walls
• Anaerobes or Aerobes• Some are Decomposers
or Pathogens• Some use conjugation• No organelles or nucleus
• E.Coli (used in genetic engenering to make insulin)
• Some used to fix nitrogen for the nitrogen cycle
• Viruses placed here for lack of a place to put them.
Plaque on teeth
Bacteria on Contact lens
What is the bacterial cell wall made of?
• Peptidoglycan (polypeptides and sugar)– Gram Positive: thick peptidoglycan
• Stains Purple• 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
Mycobacterium leprae or Leprosy
Parts of a bacteria.• All have a Cell Wall and Plasma
Membrane
• Cytoplasm, Pilli, Plasmid
• Some have Flagella and Capsules • May make Endospores when
dormant for protection.Bacterial
ConjugationDon’t Look!
Donating DNA
Conjugation:
primitive sexual method. Bacterial transformation. Discovered by Frederick Griffith 1927.
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
• 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.
Lac Operon Overview
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