I.+Viruses+(19)

= Chapter 19: Viruses = toc General Overview

media type="youtube" key="0h5Jd7sgQWY" height="315" width="560"
Table of Contents of the Video :) Lysogenic and Lytic Cycle 3:30-10:01 Retroviruses/HIV 10:10-14:09 Virus and life 2:10-3:06

General Quiz

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Some more general information about viruses with that MindBites Guy! media type="youtube" key="9Xxm5-XThdA" height="315" width="420"

= Target I: Draw and explain the general structure of a bacteriophage virus. =




 * **Bacteriophage**: a virus that infects bacteria
 * contains genetic material (DNA or RNA) in a protein coat called the **capsid,** or **head**
 * **capsids:** made out of protein subunits called **capsomeres**
 * can have **icosahedral** heads- heads that have 20 triangular facets
 * some bacteriophages have **viral envelopes**-surround capsid, contain //host cell// phospholipids and membrane proteins
 * **tail fibers**- used to attach to the bacterium they are infecting

= Target II: Why are viruses not considered living. = http://www.education.com/study-help/article/biology-help-viruses-non-living/ The above site goes over why viruses are considered to be non living and why.

First, note that the **3 requirements to be considered "living"** are: The issue is that viruses are packages of protein with bits of genetic material. They //cannot reproduce on their own// and they use other cells to insert their genetic material into and reproduce by "hijacking" the cell. They are also tinier than cells and contain only RNA or DNA, while they lack organelles, so they are //not even considered unicellular// because they lack a cell membrane too.While they can evolve through mutations, viruses lack the other 2 requirements, and as a result, are not classified as living.
 * 1) The capability of **evolution**. (Not that the organism makes itself change, but rather over time, changes occur through natural selection.)
 * 2) The organism has **cell(s)**.
 * 3) The organism can **reproduce**.

= Target III: Distinguish between lytic and lysogenic cycles of viral reproduction. Explain the process of bacterial transformation. = [] ^ A nice video about lytic and lysogenic cycles, with a quiz at the end.

A Video explaining the Lytic and Lysogenic Cycles of viruses. media type="youtube" key="wLoslN6d3Ec" height="315" width="420"

= Target IV: Explain the function of reverse transcriptase for retroviruses. = A nice video/activity to summarize. []

= Target V: Compare the size and structure of viruses to prokaryotic and eukaryotic cells. = This picture should be a general size explanation. Viruses are much, much smaller than prokaryotic cells, which are usually about a tenth of the size of a eukaryotic cells. This is due to eukaryotic cells having more complex organelles that perform more complex functions and as a result, have greater size compared to the other two. Eukaryotic cells compose diverse life forms such as animals, plants, and fungi. Meanwhile, prokaryotic cells compose bacteria. With the smaller size, there are less organelles and less functions to perform, which makes the organism unicellular. Finally, with viruses, they are merely genetic information contained within a protein wall, so they are tiny. In fact, with connection to Target II, this is a reason why viruses are not considered living. They can't even create or use energy; they only replicate using a host cell. = Target VI: Explain how viruses are categorized. =
 * The only things smaller than a virus are viroids and prions. (Diana Liao)

__Fill in the Blank:__
1. Viruses are composed of a nucleic acid enclosed in a __(1)__ and sometimes are wrapped in a viral envelope. 2. A __(2)__ phage reproduces only by the lytic cycle, and a __(3)__ phage can use both the lysogenic and lytic cycle. 3. The lysogenic cycle can become the lytic cycle when the __(4)___ exits the bacterial chromosome and initiates the assembly of new phages. 4. A defense that bacteria have against infection by a virus are (5), which cut up the foreign viral genome. 5. __(6)__ are RNA animal viruses that contain _ _ (7), an enzyme that changes ___ to__ _ (8).

__Answers:__ 1. capsid or protein coat 2. virulent 3. temperate 4. prophage 5. restriction enzymes 6. Retroviruses 7. reverse transcriptase 8. RNA to DNA

__Practice in the Structure of a Bacteriophage Virus__ Here is an unlabeled diagram I made to practice identifying the parts of a bacteriophage.

__Answers:__ A. capsid (icosahedral shape) B. Tail Fibers C. Genetic material (single- __or__ double-stranded DNA __or__ RNA) D. Sheath

Here are some quick review virus quizzes: http://biology.about.com/library/weekly/blvirus1q.htm http://highered.mcgraw-hill.com/sites/0073031208/student_view0/chapter33/multiple_choice.html http://www.proprofs.com/quiz-school/story.php?title=chapter-25-virus-quiz

A flowchart following the possible pathways of a bacteriophage, most notably the lytic and lysogenic cycles.

A quick synopsis of how exactly a bacteriophage replicates its nucleic acid within the bacteria and lyses the host cell during the lytic cycle. media type="youtube" key="8sUaxWuzmc4" height="315" width="420"