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Biology 1001A Midterm: Biology 1001A Term Test 1 Outcomes

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Biology 1001A
Scott Mac Dougall- Shackleton

• Characteristics of viruses and why they are not generally considered to be “alive”. Viruses are obligate organisms requiring a host cell for processes eg. replication, metabolism. They have a different cell structure. • Why viral infections are usually difficult to treat with drugs, and exceptions to this general principle. Viral infections are hidden inside of their host cells. Viruses that use their own polymerases however, are easier to treat and target with antivirals. eg. RNA viruses, influenza. • Whether viruses are always pathogenic Not all viruses are pathogenic as some benefit their hosts eg. bacteriophages which prevent growth such as E.coli. • Hypotheses for the evolutionary origin of viruses. Hypothesis A Hypothesis B Evolved After cells appeared Thought to be ancient, predating cells May have evolved from fragments of RNA/ DNA First, fragments become surrounded by recognition proteins. Then escape from their parent cell. They do not have a common origin. • Lifecycle of HIV Virion hooks onto Reverse Transcriptase Integrase splices DNA Transcription, New virions assemble, receptors and enters turns RNA into DNA into host DNA translation, protease bud out, enter host cell bloodstream • Characteristics of HIV that affect the prospects for drug design and vaccine development HIV is a retrovirus that uses reverse transcriptase- no proofing system= lots of mutations= difficult to design a drug to accommodate those mutations. • The general mechanisms by which vaccines protect against diseases A vaccine injects into the body a non-active part of the disease. This triggers the release of antibodies and immune cells are released to fight the disease. Memory T-cells are prepared and this trains the body to recognize the disease and how to fight it if exposed to the active disease in the future. • Why developing a vaccine against HIV is relatively challenging, compared to other diseases. Viruses have a high mutation rate. HIV is a retrovirus that uses reverse transcriptase- no proofing system= lots of mutations= difficult to design a drug to accommodate those mutations. • Why people are encouraged to get a flu vaccine each year (as opposed to one time only) The flu virus changes and adapts. Each year the flu vaccine is changed to accommodate this and fully protect people. • Major steps in lifecycle of HIV, and which of these are appropriate targets for antiviral drug design 1. Virion hooks onto receptors and enters host cell 2. Reverse transcriptase turns RNA into DNA (ERROR-PRONE) 3. Integrase splices DNA into host DNA 4. Transcription, translation, protease 5. New virions assemble, bud out, enter bloodstream • Mechanism by which AZT interferes with HIV replication AZT mimics thymidine to fool reverse transcriptase. It grabs the AZT instead of the T and therefore the nucleotide cannot attach. • Why the effectiveness of AZT decreases over time The virus becomes increasingly resistant to AZT through mutations. This is a random process that happens through mutations and occurs regardless of AZT administration. • Why wouldn’t the virus (HIV) want to prolong the life of the host to, in turn, prolong its own? In the short-term, the faster killing viruses are more effective. Natural selection does not look ahead, rather at the viral competition in the moment. • Principles underlying evolution by natural selection: variation, heritability, differential reproduction, change in genotype of the population Variation- differences btwn organisms. Heritability- Differential reproduction- change in genotype of the population • Rationale for using multiple drugs simultaneously to treat viral infections By using a drug cocktail, it is less likely that the virion will become resistant to the drug. It may become resistant to one or two drugs in the combination, but unlikely all of them. • Evolutionary origins of HIV and why the virus is much more common in some parts of the world than others The virus is theorized to have been started in chimpanzees. These primates are prevalent in Sub-Saharan Africa, and the pattern of this disease also indicates a high prevalence in the area. • Role of CCR5-d32 mutation in human resistance to HIV, and possible reasons why this mutation is more common in some populations than others CCR5 receptor is on white blood cells and acts as a “door” which allows HIV to enter the cell. When the CCR5-delta32 mutation is present, it makes the protein smaller and no longer on the outside of the cell, making it almost impossible for HIV to get in and infect the cell. It is more common in places like Europe. This mutation may have been gained from other diseases eg. bubonic plague. Or it could be a random process. • Difference between growth and development of an individual vs evolution Evolution refers to a gradual change in populations over generations. Aging is not considered to be evolution as it occurs in one individual’s lifespan. • Meaning of "vestigial structures" and what they tell us about the history of life on earth Vestigial structures are anatomical parts of organisms that are no longer being used (eg. dolphins’ fingers). These structures indicate that they were useful at some point in the organisms’ historical origins. • Meaning of "catastrophism", "gradualism", "uniformitarianism" Catastrophism- the idea that the earth has been hit w sudden catastrophies sometimes worldwide in scope (eg. layers of fossils). Gradualism- Idea that earth has changed slowly (eg. water erosion). Uniformitarianism- Geologic processes shaped Earth overtime into what we see today (eg. volcanic eruptions, movement of glaciers). • How the principles of gradualism and uniformitarianism challenge the idea that the earth is only a few thousand years old Both suggest that the Earth has been gradually changing over time. • Mechanisms of evolution proposed by Lamarck He proposed two mechanisms of evolution. a) Use/disuse: Body parts grow/ shrink in proportion to their usage. Shown to be TRUE. b) Inheritance of acquired characteristics: changes an organism acquires over a lifetime are passed down to offspring. False. • Ways in which Lamarck contributed to development of evolutionary theory
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