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Western University
Biology 1001A
Tom Haffie

Lecture 2:- Evolution in action: Human Immunodeficiency Virus (HIV) p 491-493 The HIV pandemic : Global Prevelance ofHIV: Sub-Saharan Africa Global HIV Trends (1990-2009): Number of people& children living with HIV increased Aduls and Child deaths due to HIV decreased Number of orphans due to Aids decreased Tree of Life: Where do viruses fit? HIV lifecycle: hijack immune cells AZT mimics thymidine and inhibits reverse transcriptase …but eventually stops working because of AZT resistance Evolution of drug resistance • mutations produce virions that vary in drug resistance • resistance passed from ‘parents’ to ‘offspring’ • not all virions reproduce • in the presence of the drug, resistant forms are more likely to reproduce than susceptible forms Resistance to one drug is inevitable: to many drugs is less likely Humans evolve too. CCR5-D32 allele à HIV resistance Why the mutation is distributed this way? • Selection pressure imposed by HIV • Selectively favoured in North Europe during historical epidemics (plague, small pox) • Chance and History Summary: Evolution in action • Evolution can be very fast • Even non-living things can evolve HIV evolution involves themes such as • Mutation and variation • natural selection • Evolutionary History • Humans as an evolutionary force & as the products of evoltuion LEC 2 HIV 1. The general mechanisms by which vaccines protect against diseases Attaches to the cells
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