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Viruses . Intro to viruses. http://www.brainpop.com/health/diseasesinjuriesandconditions/viruses /. What is a Virus?. Very small Non-living particle Made up of nucleic acid and proteins Can only reproduce by infecting living cells Do not carry out respiration, grow or develop. - PowerPoint PPT Presentation
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Viruses
Viruses Intro to viruseshttp://www.brainpop.com/health/diseasesinjuriesandconditions/viruses/
What is a Virus?Very small
Non-living particle
Made up of nucleic acid and proteins
Can only reproduce by infecting living cells
Do not carry out respiration, grow or develop
VIRUS STRUCTURE: THEY ALL HAVEViruses have an inner core of nucleic acid which contains either RNA or DNA
Has outer protein coat called a capsid.
Some Viruses have anEnvelope Lipid MembraneEnvelope allows for extended survival outside the cell in order to spread infection
Viruses have different shapes and sizes.
The arrangement of the proteins in the capsid of a virus determines the viruss shape
Knowledge checkWhat characteristic do viruses share with all living organisms?
Respiration Metabolism Replication Movement Knowledge CheckFill in the blanks
The nucleic acid core of a virus contains ________ or __________
All viruses contain a coat of ________ and a core of _________
Shapes and Examples- Enveloped Virus: Influenza
: InfluenzaSmallpoxCowpoxEbola
Polyhedral VirusesChicken Pox virus,Human PapillomaAdenovirus(respiratory infections, pink eye)HIV
Helical VirusesTobacco Mosaic Virus
Structure of Bacteriophage- Virus that Infects a bacteria
Nucleic Acid: DNA or RNACapsid Host Cell The cell in which a virus replicates in Before a virus can replicate it must enter a host cell
Before it can enter a host cell it must first recognize and attach to a receptor site on the plasma membrane of the host cell. The World of viruses- View and create a summary of learning paragraph.
How do viruses invade a cell
AttachInject and/ or Incorporate genetic infoReplicateAssembleLyse or Divide within host
Viral InfectionMost viruses are highly specific to the cells they infect. Ex: Plant viruses only infect plants
Bacteriophages are viruses that infect bacteriaEx: bacteriophage T4
Viruses have two ways of infecting the host cell:-Lytic Infection-Lysogenic Infection
Viruses and Diseases Viruses cause human diseases such as polio, measles , influenza, and AIDS.
Viruses attack and destroy certain cells in the body causing symptoms of the disease
The best way to prevent against viral diseases is to prevent infection through vaccination. RetrovirusesViruses that contain RNA as their genetic material
When retroviruses infect a cell they produce a DNA copy of their RNA.
Called retroviruses because their genetic information is copied backwardsFrom RNA to DNA instead of DNA to RNA
Retroviruses are responsible for some types of cancer and HIV
HIV
Lets Look at HIV in ACtionhttp://www.hhmi.org/biointeractive/disease/animations.html
Lets Watch the two types of infection on classzonehttp://www.classzone.com/cz/books/bio_07/resources/htmls/animated_biology/unit6/bio_ch18_0550_ab_virus.html
Lytic InfectionLytic Cyclevirus injects its nucleic acid into the hosttakes over the host cells metabolismcauses host cell to start replicating the viruses proteins and nucleic acids virus secretes enzymes that lyse the host cells cell wall and releases new virus particlesthese particles can attack other host cells
Lytic Infection causes host cell to be lysed and destroyed.
Lysogenic Infection Lysogenic cycleLysogenic virus injects its nucleic acid into a host cellViral DNA is integrated into the host cells chromosome called a prophageEvery time host cell reproduces, the provirus is replicated along with it every cell that originates from the infected host cell has a copy of the provirus
Retroviruses and cancerRetroviruses can cause some cancers
Retroviruses that convert, or transform, normal cells tumor viruses
These viruses carry genes that disrupt the normal controls over cell growth and division
The lysogenic cycle can take place for many years
At any time the provirus can be activated and enter a lytic cycle host cell is killed
Knowledge checkA lytic infection occurs when a
Virus infects a bacterium and kills it immediatelyVirus embeds its genome into the DNA of the host cellVirus enters a cell, makes copies of itself, and causes the cell to burstVirus inserts its DNA into the DNA of the host cell and remains part of the host cell for many generations
What is a vaccine?A preparation of a weakened or killed virus or viral protein
When injected into the body, it stimulates the immune system in an effort to create permanent immunity to the disease
For vaccines to be most effective it must be used before an infection begins.
Vaccines are used for the prevention of viral infections
Vaccines are NOT used for bacterial infectionsDiseaseSymptomIncubationMeasles Rash, fever9-11 daysShingles Pain, itching on skinYearsWartsBumpy areas on skinMonthsCoryza (cold)Sneezing, runny nose, fever2-4 daysHIVFatigue, weight loss2-5 yearsThe symptoms and incubation time of a disease can indicate how the virus acts inside its host cell.Which diseases may be caused by lytic viruses?Which diseases may be caused by lysogenic viruses?
Plant Viruses
Tobacco Mosaic Virus Was the first virus to be identified
Causes disease in tobacco plants
Knowledge CheckOne group of viruses that contain RNA as their genetic information are
Oncogenetic virusesRetrovirusesCapsidsProphages
Videoshttp://www.pbs.org/wnet/secrets/previous_seasons/lessons/lp_virus_videos.html#