viruses viruses are pathogens that attack cells from the inside. they hijack your own dna and use it...
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VirusesViruses are pathogens that attack cells from the inside. They hijack your own DNA and use it against you. A virus cannot be treated with antibiotics, it can only run its course until your immune system kicks it out.
..Even then, the virus may lay dormant within the cells and come back at a later date
Adapted from www.biologycorner.com
Adenovirus - cause of the common cold
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Properties of viruses•no membranes, cytoplasm, ribosomes, or other cellular
components•they cannot move or grow•they can only reproduce inside a host cell•they consist of 2 major parts - a protein coat, and hereditary
material (DNA or RNA)•they are extremely tiny, much smaller than a cell and only
visible with advanced electron microscopes
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Structure of DNA (review)
Shape of a DOUBLE HELIX
Each side held together by weak HYDROGEN BONDS
Repeating units of NUCEOTIDES
Sides of "ladder" are deoxyribose and phosphates
Center is A, T, G, C
A -> TG -> C *base pair rule
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nucleotide
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Virus Structure
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Parasitic Nature Obligate intracellular parasites (they cannot exist independently)Specific to hosts (human, dog, some can cross species) Specific to cells , the common cold is a virus that specifically attacks cells of the respiratory track (hence the coughing and sneezing and sniffling). HIV specifically attacks white blood cells
This is a bacteriophage, a type of virus that attacks bacteria. It is recognizeable because it looks like the lunar landing spaceship.
See animation http://www.youtube.com/watch?v=41aqxcxsX2w&feature=related
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Viral Reproduction
Lytic cycle = reproduction occurs, cells burstLysogenic cycle = reproduction does not immediately occur (dormancy)
Virulent = viruses that undergo both cycles
https://www.youtube.com/watch?v=Rpj0emEGShQ&feature=player_embedded
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1. Attachment2. Penetration - the virus is engulfed by the cell (Cell can enter Lysogenic or Lytic Cycle)3. Biosynthesis - viral components are made (protein coat, capsid, DNA/RNA)4. Maturation - assembly of viral components5. Release - viruses leave host cell to infect new cells (often destroys host)
Viruses multiply, or replicate using their own genetic material and the host cell's machinery to create more viruses. Viruses cannot reproduce on their own, and must infect a host cell in order to create more viruses.
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Lytic vs Lysogenic Pathways of viruses
Starring the phage named Lambda
See: http://highered.mcgraw-hill.com/sites/007352543x/student_view0/chapter20/lambda_phage_replication_cycle.html
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Retroviruses -- RNA viruses that have a DNA stage •Human Immunodefiency Virus - causes AIDS •Retrovirus (RNA inside a protein coat) •Reverse Transcriptase makes DNA from the virus RNA •DNA inserts into host DNA •Proteins are assembled from the DNA code •Viruses assembled from the proteins •Viruses released from the cell
(Link) HIV Animation - how virus infects cells
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Developing a vaccine for AIDS is difficult because it is a RETROVIRUS. RNA mutates easily and each individual virus can be slightly different from the others. In fact, different viruses can exist within the same person.
See: HIV coloring
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Emerging Viruses illnesses not previously known
AIDS, West Nile Virus, SARS, Ebola, Bird Flu
•Could be mutations of known viruses •Could be viruses exposed when new areas were developed •Could have jumped species (avian flu, swine flu)
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Related to Viruses
Viroids - even smaller than viruses, consist of RNA strands that lack a protein coat
Prions - "rogue protein", believed to be the cause of Mad Cow Disease, also may cause Kuru in cannibal tribes
See: http://highered.mcgraw-hill.com/sites/007352543x/student_view0/chapter20/how_prions_arise.html
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How Do Vaccines Work?
1. Once you have gotten a virus, such as chicken pox, your body develops the immunity to that virus.
2. Vaccines are made by growing a weakened or killed form of the virus (often grown in eggs)
3. This form of the virus is injected into a person's body, which causes an immune response, and immunity to the virus.
- Remember Jenner's cowpox vaccine?
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RV = rotovirus; DTaP = diptheria, tetanus, pertussis (whooping cough); Hib = haemophilus influenza type B; PCV = pneumococcal vaccine; IPV = inactivated polio virus; MMR = measles, mumps, rubella,
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INFLUENZA
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BACTERIOPHAGE
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H1N1
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SMALLPOX
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