Anatomy and Physiology Answer Key

3 aids sufferers develop a range of debilitating

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Unformatted text preview: wing the supply of fresh (high oxygen) air while expelling high carbo dioxide air (CO2 gained as a result of gas exchanges in the tissues). 2. (a) Quiet breathing: External intercostal muscles and diaphragm contract. Lung space increases and air flows into the lungs (inspiration). Inflation is detected and breath in ends. Expiration occurs through elastic recoil of the ribcage and lung tissue (air flows passively out to equalize with outside air pressure). (b) During forced or active breathing, muscular contraction is involved in both the inspiration and the expiration (expiration is not passive). 3. Water vapour 4. The elasticity of the lung tissue enables natural recoil of the lungs during quiet breathing so that expiration is a passive process not requiring energy. 5. Blood pH is a good indicator of high carbon dioxide levels, since increased CO2 levels cause blood pH to fall. This indicates a need to increase respiratory rate to remove the CO2 (and obtain more oxygen). Gene amplification is used to make multiple copies of the normal (corrective) allele. 4. Breathing in Humans (page 160) Transfection of (and correction of the genes in) germline cells allows the genetic changes to be inherited. Note: In this way, a heritable disorder can be corrected so that future generations will not carry the faulty gene(s). Transfection of somatic cells only corrects those cells for their lifetime. 3. 5. (a) X-linked SCID is caused by a mutation to a gene on the X chromosome encoding the common gamma chain. ADA SCID is caused by a defective gene that codes for the enzyme adenosine deaminase. (b) The recipient's marrow is often depleted first so that the new (corrected) marrow cells predominate and can proliferate in preference to Potential risks include: The genes may integrate randomly into chromosomes and disrupt the functioning of normal genes (this occurred recently in retroviral vectors used in SCID gene therapy patients). In the case of viral vectors, the host can develop a strong immune response to the...
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