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Biology, outcomes first term

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Biology 1001A
Tom Haffie

STUDY OUTCOMES FOR OCTOBER BIOLOGY MIDTERMLECTURE TWOGeneral mechanisms by which vaccines protect against diseasesThey help increase the original protection Longterm immunity is conferred by the maintenance ofAntigenspecic immune effectors andor by the induction of immune memory cells that may be sufciently efcient and rapidly react that your immune system already has Vaccines usually consist of weak versions of viruses or dead ones in order prepare the memory cells in your body to be able to fight the virus when it recognizes it Why people are encouraged to get a flu vaccine each year as opposed to one time onlyYou are encouraged to get a flu vaccine each year because they tweak it so that it fights the most commonrecent strain of the flu thats going on This way it ensures you that you have protection even if the virus has gone through a mutation General global distribution of HIV infections60 of all cases which is more than the rest of the world put together are found in SubSahara Africa Which out of these 90 are children under 15 years of age This is then followed by South and SouthEast Asia then North America Eastern EuropeCentral Asia along with CentralSouth America WesternCentral Europe East Asia Caribbean followed by Oceania General temporal trends in HIV infection rates The number of people living with aids has increased but seems to be hitting a plateauDeaths due to aids seem to have decreased possibly due to advances in medicine and antiaids therapiesNumber of children orphaned due to parents dying from AIDS is still increasing Number of children living with HIV is increasing but seems to be hitting a plateauFactors that explain why no cure or universal vaccine has been developed for HIVAIDS Fast mutations new disease a lot of money different strains of the virus its a retrovirus Nobody has ever recovered from HIV infection so there is no natural mechanism to imitateHIV destroys the immune system cells that are meant to fight against itSoon after infection HIV inserts its genetic material into human cells where it remains hidden from the immune systemHIV occurs in several subtypes each of which is very different from the othersEven within each subtype HIV is highly variable and constantly changingThere are no good animal models to use in experiments although the use of nonhuman primate NHP models could become a more significant model for HIV vaccine design and testing in the future Why developing a vaccine against HIV is relatively challenging compared to other diseasesIts challenging for various reasons1 our bodies dont have a natural defense for it its a fairly new disease only known about it for 35 years therefore no immunizations 2 Its a very fast mutating virus thus its next toimpossible to find a cure that will protect you against every strain of this virus 3 Business aspect companies make a lot more money off of treatments than cures 4 Its a retrovirus Reasons why viruses are not considered aliveBecause they cannot SELFreproduce They need a host because they are considered obligate parasites They dont have their own metabolic processes because they arent cell based a necessary condition of living beingsReasons why antiviral drug therapies often have serious side effectsBecause the virus uses every part of the host cellits metabolism physiology etc when the antiviral goes to kill the virus it will also attack and cause collateral damage by taking out host cells and tissues Major steps in life cycle of HIVHIV can infect multiple cells in your body its main target is the CD4 lymphocyte also called a Tcell or CD4 cellBinding and Fusion This is the process by which HIV binds to a specific type of CD4 receptor and a coreceptor on the surface of the CD4 cell This is similar to a key entering a lock Once unlocked HIV can fuse with the host cell CD4 cell and release its genetic material into the cellReverse Transcription A special enzyme called reverse transcriptase changes the genetic material of the virus so it can be integrated into the host DNAIntegration The virus new genetic material enters the nucleus of the CD4 cell and uses an enzyme called integrase to integrate itself into your own genetic material where it may hide and stay inactive for several yearsTranscription When the host cell becomes activated and the virus uses your own enzymes to create more of its genetic materialalong with a more specialized genetic material which allows it make longer proteinsAssembly A special enzyme called protease cuts the longer HIV proteins into individual proteins When these come together with the virus genetic material a new virus has been assembledBudding This is the final stage of the virus life cycle In this stage the virus pushes itself out of the host cell taking with it part of the membrane of the cell This outer part covers the virus and contains all of the structures necessary to bind to a new CD4 cell and receptors and begin the process againREVERSE TRANSCRIPTION IS HIGHLY ERRORPRONE thus causes mutations Specific role of integrase and reverse transcriptase in retroviral life cycleIntegrase is a viral protein out of the 9 that has several roles After the completion of reverse transcription of the viral RNA genome into DNA it appears in part to be responsible for ferrying the viral DNA into the nucleus of the cell a position where it has the ability to closely associate with one of the chromosomes of the host cellSubsequently integrase catalyzes the insertion or integration of viral DNA into the host cellular DNA a step of the viral lifecycle required for reprogramming the cell to produce more copies of itself HIV1 integrase is a member of a protein superfamily known as the polynucleotidyl transferases It has an ancient and highly conserved catalytic domain described not only in human retroviruses but also found in the retrovirallike elements of the fruit fly Drosophila and yeast and even exists in certain primitive transposons found in bacteriaReverse transcriptase is specific to virus and isnt a part of a host cells life cycle Because a retrovirus store their information in the form of RNA they have to go through reverse transcription which is highly error prone in order to integrate itself into a host chromosome and parasitize it
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