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Chap 1 lec - shows heritable variation in survival and...

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1/19/09 Evolution is change over time- why and how? Biological evolution is change in allele frequencies in a population over time---microevolution the process of descent with modification and divergence by which multiple species arise from a common ancestor---macroevolution both part of change -discovering and describing diversity—how many, how related? -processes shaping biological diversity—origin of novel traits, what limits biological diversity? The evolution of HIV AZT-short term success, but long-term failure?? Selection thinking origin of HIV tree thinking retrovirus -genetic material RNA, viral replication requires intermediary DNA phase— retrotranscription (retrotranscriptase) AZT blocks retrotranscription-blocks active site of enzyme at first was very effective—viral load reduced 50% at .01 uM. 2 yrs later, 50% reduction at 10 uM 2000 fold increase in resistance. When AZT treatment stopped, resistance back to original level. Selection thinking-evolution by natural selection is expected and automatic when a population
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Unformatted text preview: shows heritable variation in survival and reproduction. HIV infections are heterogeneous-extremely variable b/c retrotranscription is error-prone process. May have mutant retrotranscriptase AZT resistance has a genetic basis- passed from parent virions to offspring survival and reproduction—host immune response, rate of replication, ability to invade 1/22 in the prescence of AZT, % resistant virions will increase—why the reversal??? changed to context of evolution-select for forms with survival advantages. AZT resistance comes at a cost-they were less fit before AZT used. WhenAZT treatment is stopped, conditions change and proportion of diseased cells decreases. Evolution is shortsighted-it doesn't “know” where it is going. Context dependence. Origin of HIV-tree thinking. Immunodeficiency does not always affect an animal adversely. Can be asymptomatic. phylogentics...
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