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Western University
Biology 1001A

Lecture 2 HIV1General mechanisms by which vaccines protect against diseasespretrains body for virusesinfects body with a little bit of the virus so that memory cells in body can quickly deploy the correct antibodies and mechanisms to defend against diseases2Why developing a vaccine against HIV is relatively challenging compared to other diseasesmutations of HIV is fast and often changes so much that anti bodies no longer recognize the viruschanges shape quickly so anti viruses can no long latch on the necessary sites3Why people are encouraged to get a flu vaccine each year as opposed to one time onlyflu virus also changes quickly and there is a lot of variation from year to year such that last years vaccine is essentially useless on this years4General global distribution of HIV infectionstotal of 34 million to date with 225 million in sub Saharan Africa 4 1 million in Asia5General temporal trends in HIV infection ratesnumber of people with AIDsHIV children with HIV children orphaned by HIV plateauing and death due to HIVAIDs decreasing 6Factors that explain why no cure or universal vaccine has been developed for HIVAIDSconstantly mutatingchanging shapeobligate cellular parasiteproduct of around 30 years of evolution7Reasons why viruses are not considered alivedo not have cells and are not selfsufficient must invade a host cell in order to survive8Reasons why antiviral drug therapies often have serious side effectsdue to the obligate cellular nature of HIV it is not possible to take out the virus without taking out the host cell as the virus uses mostly the host cells enzymes and proteins9Major steps in life cycle of HIV10Specific role of integrase and reverse transcriptase in retroviral life cycleintegrase allows the DNA of the retrovirus to be integrated into the DNA of the host cellreverse transcriptase firstly makes DNA molecule from RNA molecules and then creates the complementary pair to the first strand of DNA molecule for the virus11Mechanism of action of AZTsimilar to that of the nucleotide when AZT is used by reverse transcriptase during transcription it inhibits the transcription process and thus the new double stranded DNA cannot be completed12Reasons why effectiveness of AZT decreases over timethis is because as the drug is being used only the viruses with the genetics that are resistant to the drug can be reproduced as the others will be wiped out Thus after a couple of cycles all of the replicated virus DNA will be resistant to AZT13Rationale for multidrug drug cocktail approach to treating viral infectionsthe idea is that it is far less likely for a virus to develop immunity to several drugs at once thus most patients are encouraged to take a cocktail of drugs to combat HIVAIDs14Principles of evolution of HIV variation heritability differential reproduction change in genotype of populationvariation occurs because of the constantly mutation nature of the HIV moleculecertain resistances should they be deemed useful are passed on from parent to offspringin the presence of drugs resistant viron are more likely to reproduce causing the viral population to change over time15Roles of CCR532 mutation in human resistance to HIV infectionthis specific mutation has a deletion that makes their receptors smaller thus people with this allele are less likely to be affected by the virus16Global distribution of the CCR532 allelemostly present in EuropeScandinavian population very little in Africa17Likely explanations of modern distribution of CCR532 alleleselection pressure has already been imposed not on humans but millions of years before on chimpsalready selected for during historical pandemics such as small pox and the plaguerandomLecture 3 The Origin of Life1Characteristics shared by all lifedisplays orderharness and utilize energyreproducesresponds to stimulushomeostasisgrows and developsevolves2Way in which properties of life are emergentcome from smaller units of lifeeg Ability to harness energy comes from use of molecules proteins and membranes but individually none of these exhibit such a characteristicadds up to the characteristic3Characteristics of the habitable zone of a solar systemunique location to the sun allows water to exist in the liquid state4Conditions of a primitive Earthlack of O2 and ozone
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