Phylogenies Phylogenetics technique tool for reconstructing evolutionary history or relaitonships based upon common ancestry o Fossil record shared internal external characteristics gene sequence Represented by phylogenetic tree cladograms Example of a phylogenetic tree Boxes will include a trait that makes the organism higher on the ladder different from the ones below it on the ladder All organisms above the box will have the trait Shark Jaw Lamprey Common Ancestor Example This tree shows that the Lamprey and the Shark had a common ancestor The box in between them contains the mapping trait jaw This means that the shark is different from the lamprey because the shark has a jaw and the lamprey does not All other organisms above the shark on the tree will have a jaw CHAPTER 27 Viruses Very small very diverse morphology Characteristics all viruses have 1 All contain either RNA or DNA genetic material 2 All possess a capsid a Outer protein covering encasing genetic material b Example Helical Capsid RNA c Example Icosahedral Capsid DNA Bacterial Virus bacteriophage DNA Capsid o Infects bacteria o Icosahedral head o Helical Tail Classic Flu Virus o Genetic material RNA o Capsid o Envelope studded with antigens used to recognize and enter appropriate host cell or to exit cell Animal Virus influenza o Helical capsid with envelope Bacteriophages 1 Lytic cycle a Replication 2 Lysogenic cycle a Resting stage Lytic Cycle 1 Attachment 2 Penetration a Host recognition a Penetrate cell wall membrane inject DNA into cell a Viral DNA hijacks the cellular replication machinery of bacterium a New virions are put together from pieces and parts of newly synthesized material a Cell lysis ruptures and new virions are released 3 Synthesis 4 Assembly 5 Release Lysogenic Cycle 1 Complex set of cues tells it to go into the lysogenic cycle Integration a Viral DNA integrates into bacterial genome prophage 2 Propagation 3 Induction a Viral DNA replicated along with genome b Something happens to move it back into the lytic cycle a Viral DNA become active and goes into lytic cycle b Examples of triggers Cell stress starvation toxins environment Phage Conversion Bacterial cell host becomes virulent infectious toxic following bacteriophage infection Lysogenic cycle o Some portion of viral DNA is expressed Production of toxin Becomes an infectious bacteria Examples Salmonella and Diphtheria When not infected by virus the bacteria is harmless has no toxin and is not infectious When it goes through phage conversion it becomes infectious and toxic o Cholera toxin degrade toxin Bacteria replicate rapidly and colonize the small intestine Causes diarrhea vomiting dehydration and death Flood infected organism with bacteria infected by viruses o The new infected bacteria will kill the bad bacteria Also done through lysin therapy o Enzymes derived from viruses that break down bacterial cell walls Vibrio Cholerae Phage Therapy
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