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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