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#