Biology Homework Chapter 10: Viruses and Bacteria
Textbook assignment: Chapter 10: Molecular Biology of the Gene, sections 17-23.
- 10.17 This section introduces the anatomy, reproductive cycle, and function of the virus. Viruses are incomplete organisms that require the DNA or RNA of their host to reproduce. Note that this is different from the way a parasite, containing its own complete reproductive information, uses a host as a habitat.
- 10.18 Viruses can cause disease by reprogramming host cells to reproduce more viruses, diverting cell resources from functions critical to the health of the cell.
- 10.19 New viral diseases emerge when viruses mutate, jump species, or find their way into the general population from a previously isolated host species.
- 10.20 Retroviruses viruses (such as AIDS) use an enzyme called reverse transcriptase to make DNA from RNA. This is "backwards" information flow, and disrupts the source information for the host organism.
- 10.21 RNA fragments or viroids, and protein fragments called prions can reproduce in host cells, creating degenerative nerve diseases or aberrant growth patterns.
- 10.22 Bacteria can gain new DNA segments through transformation (picking up a strand from the environment), transduction (injection of DNA from a previous host by a phage), and conjugation (direct swapping of DNA through sex pili with another bacteria). These forms of genetic material transfer are considered a type of asexual reproduction.
- 10.23 It is relatively easy to splice a DNA segment into the circular DNA strand of a bacteria (integrated F Factor), or transfer it as a separate circular strand (F Factor plasmid), where it can then be expressed by the bacteria's normal physiological processes. Does the virus you chose replicate by reading the host cell DNA or RNA to make its own genome? Does it replicate in the cell or invade the nucleus? Does it inject its own genome into the host DNA, or replicate separately from the host?
Read the following weblecture before chat: DNA Structure and Gene Inheritance
Take notes on any questions you have, and be prepared to discuss the lecture in chat.
Perform the study activity below:
Launch the Virus Explorer at HHMI BioInteractive.
- Observe the shapes and surface features of the viruses, then click on "show relative sizes" to note the variation in virus sizes. Which is the largest virus in this collection? Which is the smallest?
- Use the Envelope classification to identify which viruses have envelops and which don't. Do all viruses with envelopes share other features (spikes, shape)?
- Examine the hosts each virus infects. Are there any viruses unique to plants that don't attack animals? Are there viruses that attack mammals other than humans, but not humans? Are there viruses unique to humans? Are there viruses that only attack bacteria?
- How does RNA differ among viruses?
- Which viruses are transmitted by contact with a sick human or mammal? Which viruses can cross species (animal to human, plant to plant)?
- For which viruses do we have a vaccine?
- Follow up for any particular virus that interests you. Use the detail button (plus sign below name) to view a more detailed 3D model of the virus, as well as cross-section details and an outline of how the virus replicates. Read the description
- Required: Complete the Mastery Exercise with a score of 85% or better.
- Optional: Test yourself with the textbook multiple choice questions and note any that you miss that still don't make sense. Bring questions to chat!
- Go to the Moodle and take the quiz for this chapter.
Read through the lab for this week; bring questions to chat on any aspect of the lab, whether you intend not perform it or not. If you decide to perform the lab, be sure to submit your report by the posted due date.
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