Genetics of Viruses and Bacteria

1. Genetics of Viruses and Bacteria Ch 19 & 20 Everything you need to know about viruses.

2. 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

3. How the flu Changes. 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 Antigenic Shifts Avian Flu PBS

4. The Bacteriophageor Phage • Viruses that attack bacteria

5. Viruses: Are They Alive? T4 Invasion

7. 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.

8. Viral Shapes Fig 19.3

9. Grouping VirusesFig 19.1 • Presence of a Capsid and Envelope • Whether they contain RNA or DNA • Shape

12. 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

13. HIV is a retrovirus: uses reverse transcriptase. Provirus: integrated viral DNA

14. 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.

15. The Lysogenic Cycle The Lysogenic Cycle

16. Phage Lytic cycle details. • DNA replication produces more viral DNA • Transcription and translation produce protein coats and glycoprotein spikes

17. The Lytic Cycle

19. 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.

20. 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

21. 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.

22. Prions cause scrapie in sheep, mad cows disease, and Creutzfeld-Jakob disease in humans Good review Clips Of General Concepts

24. 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

25. 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

26. How are bacteria named? Group Arrangement: Strepto= Chains Staphylo= Clusters Shape:

27. 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 Conjugation Don’t Look!

28. Conjugation:primitive sexual method. Bacterial transformation. Discovered by Frederick Griffith 1927. Donating DNA

29. 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 enough that mutations show up quickly.

30. 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

31. What is an Operon? • A set of genes found in bacteria and phages that combined with the promoterand 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.

32. Operon Operations Lac Operon Overview • Terms to know: • Promoter: RNA polymerase binds to this region of the DNA • Repressor: binds to operator preventing RNA polymerases attachment. Noncompetitive inhibition. • Operator: Where the repressor attaches at the start of the bacterial operon. The AP Version of the Lac Operon

33. 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.

34. 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 off when tryptophan levels are high, negative feedback. Tryp Operon

35. 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.