#1) A few tens of thousand base-pairs length of DNA (or RNA) with a layer ofproteins wrapped around its outside (and maybe also a layer of membrane wrapped around that!) Suppose that the proteins have some mechanism to get the DNA into cells of some bacteria, or some animal plant. (usually species specific)
Suppose that this DNA gets copied in the host cells; And that some of these proteins form a layer around the DNA copies, and the copies + proteins get released by the host cells. That would be the life cycle of a typical virus. #2) Many diseases are caused by viruses: examples include: influenza, measles, smallpox, AIDS, colds
#3) Viral diseases are not treatable by antibiotics; The immune system, and its stimulation by vaccines, is our main defense against viruses.
#4) Some viruses use single stranded DNA as their genetic material In one group of viruses, the original virus has RNA, but also produces enzymes that make DNA with the same base sequence. "Reverse transcriptase" is the name of this enzyme. The AIDS virus does this.
#5) All viruses have protein capsids: some also have membrane envelopes around the outside.
#6) Some virus DNA sometimes gets inserted into the chromosomes of the host (animal or bacteria); #7) How do viruses evolve?: two theories; both might be true.
b) Escaped, run-away genes. like transposons, plasmids
often they have crossed over from some other species. AIDS from Chimpanzees and a certain species of monkey new stains of Influenza: ducks -> pigs -> humans Evolution within one species tends toward doing less harm to host.
#9) There are species of virus in bacteria, animals and plants. #10) in sea water, etc. there seem to be many more virus particles than any other (living) things. ------------------------------------ Study Questions 1) Name at least three human diseases that are caused by viruses
2) Which of the following do viruses use to carry their genetic information? double stranded DNA, single stranded DNA, double stranded RNA, single stranded RNA
3) Do antibiotics like penicillin or erythromycin help to cure viral diseases?
4) The layer of proteins that is the outer surface, or part of the outer surface of a virus is called what? 5) What are two very different theories about the origin of viruses? *6) For either or both theories, how would you explain the evolution of those kinds of viruses that use RNA as their genetic material? **7) Might these RNA viruses be related to the original beginning of the first life forms?
8) Do viruses infect animals but not plants; plants but not animals; both plants and animals and also procaryotes?
*9) Only the following regular 3-D shapes are logically possible (in which all the surfaces are regular polygons):
b) the tetrahedron, whose surface is 4 triangles c) the octahedron, whose surface is 8 triangles d) the dodecahedron, whose surface is 12 pentagons e) the icosahedron, whose surface is 20 triangles Figure out why. What's the evolutionary advantage to having the shape of an icosahedron? 10) Where did the AIDS virus get started? 11) Do viral base sequences ever get copied into the genome of the host organism? If so, what are these viruses called? |