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Biology Notes for Midterm

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Biology 1001A
Tom Haffie

10272012 94200 AM Lecture 2September 13 Evolution in action Human Immunodeficiency VirusLecture Questions Principles of evolution of HIV variation heritability differential reproduction change in genotype of population Mutations produce virions that vary in drug resistance Resistance is passed from parents to offspring Not all virions manage to reproduce In presence of a drug resistant forms are more likely to reproduce than nonresistant ones This leads to an ongoing change in genotype and phenotype of the population until entire population is resistantGeneral global distribution of HIV infections Least commonCanada US Western Europe Most Common South Sahara dessert 60 225 millionAfrica BotswanaEpidemics are disease outbreaks not confined to a particular place thats when they are called pandemics and are felt globallyHIVclassic example every continent associated with aids1980Not equally felt uniformly General temporal trends in HIV infection rates Less than 1 of Canadian adultsStats GraphMap from Slides The Hiv Pandemicover last 20 years graphsProportion of Kids under 15 who are HIV positive 90south Saharan AfricaRadical life expectancy of someone born in 1993 43years oldTotal people affected 333 million of children with HIV plateauingdeath to to AIDSdecline of people affected with HIV increasinglittle plateauPeople with AIDSdecreasing of orphans due to AIDSincreasing Biology Notes Factors that explain why no cure or universal vaccine has been developed for HIVAIDSHIV keeps evolving treatments only work temporarilyConspiracy Theory More Lucrative to make Treatments as opposed to CureBody doesnt have any natural defense against itIt varies and there are multiple strains we would need a general vaccine Tree of life Where do viruses fitLife Phylogeny representing evolutionary relationships between every living thing on earthAnimals are a tiny twig on Eukaryotes ArchaebacteriaExtreme EnvironmentsTrue Bacteria Reasons why viruses are not considered alive Viruses do not fit on the Tree of life since they are not livingThey cant self reproduce unless they have a hostThey dont have metabolic processesAre not made of cellsusually a necessary condition to consider as livingPathogen Reasons why antiviral drug therapies often have serious side effectsVirosphere They are obligate cellular parasitesneed host cells physiology o So antiviral therapy often has serious side effectso Antiviral drugs they have severe side attacks because it uses your own infrastructure you cant kill virus without killing a lot of your own tissues DNARNAProteinCentral Dogma of BiologyDirection that info flowsFrom Replication to Transcription to Translation o One way street Retroviruses like HIV do not store their genetic information in the form of DNA but in RNA 2 Biology NotesThe difference is it goes through reverse transcription o No proofreading enzymes o High rate of error lots of mutation high mutation rate o Still goes through central dogma its just an extra step at the beginningReverse transcriptionsynthesizes DNA with RNA Million times higher than mutation rate of human Major steps in life cycle of HIVSpecific role of integrase and reverse transcriptase in retroviral life cycle HIV lifecycle hijack immune cells Diagram Viral particlemuch smaller than hosts immune cellFuses to the host cell and puts its genome into the host cell o The genome is very small it codes for like 9 proteins it uses the host for pretty much everything elseOne of the Viral Enzymes Reverse Transcriptase converts the RNA to DNAIntegrase splices viral DNA into host DNATranscriptionTranslationnew virions assemble and bud off or lyse kill host cell outImmune system collapses In replicating itself the virus it kills host immune cellsIndividual usually succumb to a second infection due to weakened immune system Pneumonia or TuberculosisAnti Retroviral Therapies inhibit virusspecific enzymesGoal is to inhibit steps in the life cycle which are specific to the virusInhibit reverse transcriptase Mechanism of action of AZT AZT mimics thymidine and inhibits reverse transcriptasea step that matters to HIV but not hostAZT stands for Azedothymidine which is similar in structure to thymidine It cause HIV to grab the AZT chemical instead this chemical stalls it since it does not have an attachment site for the next nucleotide Reasons why effectiveness of AZT decreases over time3
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