Anatomy and Physiology Answer Key

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Unformatted text preview: om infection. By knocking out the immune system, it leaves the body vulnerable to invasion by microbes that would not normally infect a healthy person. 2. (a) The virus rapidly increases in numbers within the first year of infection, followed by a large drop off in numbers in the second year. Over the next 3-10 years, the HIV population gradually increases again. (b) The helper T cell numbers respond to the initial infection by increasing in numbers. After about a year, their numbers steadily decrease as they are attacked and destroyed by the HIV. 3. Transmission of HIV, (a)-(c), any three of: Blood or blood products, vaginal secretions, breast milk, across the placenta, shared needles among intravenous drug users (contaminated with blood from other drug users), sexual intercourse: both homosexual (especially between males) and heterosexual (between men and women). 4. HIV positive: Blood tests have detected the presence of HIV in blood samples from a person (even though they may not have exhibited any symptoms). 5. Blood donated by the public and used to obtain a blood clotting factor (Factor VIII) for hemophiliacs was contaminated with HIV from donors already infected with the virus. This is particularly the case in countries where people are paid to donate blood. 6. As a provirus, the viral DNA may remain latent (unexpressed) and replicate along with the host’s DNA for some time before becoming active and transcribing its genes. This has implications for the host too, who may be unaware of infection and remain symptomless (the HIV provirus may lie dormant within Biozone International 2009 Photocopying Prohibited 25 Stem Cell Technology (page 149) Animal to human organ transplants (xenotransplants). Issues can be categorized into those associated with animal welfare and those associated with risks to humans (individuals or the wider community). FOR: • Transplants from animals would relieve some of the pressure on the human organ waiting list. AGAINST: • Xenotransplants are not very compatible with human tissues; rejection rates are still unacceptably high, even from GE animals (usually pigs). • Xenotransplants involve genetic engineering of animals to produce human proteins that are more acceptable to the recipient. GE c...
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