Viruses!

Agenda- 3/18/2015Kahoot: Take out an electronic device and sign on to kahoot.itNotes on VirusesHomework: Taxonomy Quizzes (2) due Friday @ midnight!!!

Check Your Prior KnowledgeTrue or False: Viruses are larger than bacteria.

Check Your Prior KnowledgeTrue or False: Viruses can only infect animals.False, viruses can infect organisms of any kingdom.

Check Your Prior KnowledgeTrue or False: Viruses are responsible for all diseases.

Recall that bacteria are prokaryotes with cells much smaller and more simply organized than those of eukaryotes.Viruses are smaller and simpler still.VirusAnimal cellBacteriumSize Matters

Scientists were able to detect viruses indirectly long before they were actually able to see them.

The Hunt For Virus?

The Discovery of VirusesTobacco mosaic disease stunts the growth of tobacco plants and gives their leaves a mosaic coloration.It was discovered in 1930 by Wendell M. Stanley.A Nobel Prize was won in 1946 for this discovery!

What is the definition of Living?To be considered alive, an organism must:Be made of at least one cell.Be able to grow and reproduce independently.Have information stored in DNA.

The big question:Do viruses fulfill these criteria?

The Big QuestionsDo viruses fulfill these criteria?

Are viruses made of at least one cell?

What Is A Virus?VIRUSES ARE NOT CELLS!!!

Viral StructureViruses are very small infectious particles consisting of nucleic acid enclosed in a protein coat and, in some cases, a membranous envelope.

Viral StructureAt the most basic level, viruses can be classified as segments of nucleic acids contained in a protein coat.

Parts Of A VirusThe nucleic acid found in a virus can be either RNA or DNA, but cannot be both.

HIV has an RNA genome.Varicella zoster (the chicken pox virus) has a DNA genome.

Parts Of A VirusA capsid is the protein coat that encloses the viral genome and can have various structures.

Parts Of A VirusSome viruses have an envelope that surrounds the capsid and helps the virus enter cells. It is derived from the hosts cell membrane and includes glycoproteins.

Virus ShapesViruses exist in many shapes. Thread-like - Ebola.

Virus ShapesViruses exist in many shapes. Spherical - Influenza.

Virus ShapesViruses exist in many shapes. Rods - Tobacco Mosaic Virus.

Virus ShapesViruses exist in many shapes. Polyhedral - Adenovirus.

Virus ShapesViruses exist in many shapes. Hard to classify shape - Bacteriophage.

The Big QuestionsDo viruses fulfill these criteria?

Are viruses made of at least one cell?

The Big QuestionsDo viruses fulfill these criteria?

Are viruses able to grow and reproduce independently?

Viral ReplicationIn short, viruses can reproduce ONLY by infecting living cells.

Two Methods of Viral ReproductionLytic CycleLysogenic Cycle

The Lytic CycleThe lytic cycle is a reproductive cycle that culminates in the death of the host.The virus produces new viruses and digests the hosts cell wall, releasing the progeny viruses.https://www.youtube.com/watch?v=rzdwfwuVWUU

Lytic Cycle

Lytic Cycle

The Lysogenic CycleThe lysogenic cycle replicates the viral genome without destroying the host.The viral DNA is replicated, but new viruses are not made during the lysogenic cycle. New viruses are only made during the lytic cycle!A virus in the lysogenic cycle may come out of dormancy and enter the lytic cycle.

The Lysogenic Cycle

The Lysogenic Cycle??? What is this???

What Is A Provirus?After the viral nucleic acid is inserted into the cell, it may be integrated into the cells DNA. When the viral DNA are integrated into the cells DNA, it is known as a provirus.

The Lysogenic Cycle

The Big QuestionsDo viruses fulfill these criteria?

Are viruses able to grow and reproduce independently?

The Big QuestionsDo viruses fulfill these criteria?

Do viruses have information stored in DNA?

Lets Review: Parts Of A VirusNucleic acid (RNA or DNA), capsid and envelopes on some viruses.

HIV has an RNA genome.Varicella zoster (the chicken pox virus) has a DNA genome.

RetrovirusesSome viruses, such as HIV, have RNA as their genetic material instead of DNA.HIV is known as a retrovirus. Retroviruses work very differently than other viruses.

RetrovirusesRetroviruses replicate their nucleic acids in reverse using an enzyme called reverse transcriptase. This enzyme that allows them to transcribe RNA to DNA, instead of DNA to RNA like normal.

RetrovirusesThe newly transcribed DNA is then integrated into the hosts DNA as a provirus!Viral RNA enters the host cell.1Viral RNA is reverse transcribed into DNA.2Viral DNA is integrated into the host cells DNA, creating a provirus.3Host cell replicates the viral DNA (lysogenic cycle).4

The Big QuestionsDo viruses fulfill these criteria?

Do viruses have information stored in DNA?

SoAre Viruses Living?To be considered alive, an organism must:Be made of at least one cell.Viruses are not made of cells.Be able to grow and reproduce independently.Viruses do not grow and reproduce independently.Have information stored in DNA.Viruses have information stored in DNA or RNA.

Are Viruses Living?No!!!!

Viruses are not considered alive because they are not made of cells and they do not grow or reproduce on their own.

PathogensA pathogen is anything that can cause you harm.Viruses are pathogens, or agents that cause disease.Viruses can cause disease in all living things including in bacteria, fungi, protists, plants and animals.Because they cause disease, viruses have a major impact on the living world.

Viral DiseasesAIDS - Acquired Immunodeficiency SyndromeCaused by Human Immunodeficiency Virus.transmitted through direct contact of a mucous membrane or bloodstream with blood, semen, vaginal fluid, pre-seminal fluid, and breast milk. The virus kills the Helper T Cells of the immune system.

Viral DiseasesAIDS - Acquired Immunodeficiency SyndromeCaused by Human Immunodeficiency Virus.

HIV can be transmitted by: All types of sex.Dirty needles.Blood Mother to child during pregnancy and/or childbirth.Breastfeeding.

Viral DiseasesAIDS - Acquired Immunodeficiency SyndromeCaused by Human Immunodeficiency Virus.

There is no cure or preventative vaccine available.

Viral DiseasesCommon ColdSymptomsSinus congestion, muscle aches, cough, fever and sore throat.Transmitted by inhalation or direct contact.

Viral DiseasesEbolaSymptomsHigh fever and uncontrollable bleeding. Transmitted through bodily fluids.

Viral DiseasesInfluenza (flu)SymptomsFever, chills, fatigue, cough, sore throat, muscle aches, weakness and headache. Transmitted by inhalation.

Viral DiseasesMumpsSymptomsPainful swelling in salivary glands. Transmitted by inhalation.

Viral DiseasesPolioSymptomsFever, headache, stiff neck and possible paralysis. Transmitted by fecally contaminated food or water.

Viral DiseasesRabiesSymptomsMental depression, fever, restlessness, difficulty swallowing, paralysis and convulsions. It can be fatal. Transmitted by the bite of an infected animal.

Viral DiseasesSmallpoxSymptomsBlisters, lesions, fever, malaise, blindness and disfiguring scars. It was often fatal. Transmitted by inhalation.Eradicated in 1979.

Viral DiseasesChicken pox (varicella- zoster virus)SymptomsA fever, feeling sick, tired, and sluggish, little or no appetite, headache, sore throat and itchy rash.Transmitted through the air via a cough or sneeze.

What are Vaccines?Vaccines are a weakened or killed form of the virus.By injecting this into the body, your body will build antibodies towards this particular virus.

What are Vaccines?When your body is infected with the real virus, you already have the antibodies to fight itVaccines are used for prevention only! They cannot do anything to fight a virus if you are already infected.

Special Types of Viruses And Their Relatives

Viruses That Only Infect BacteriaA bacteriophage is a special type of virus that only infects bacteria. The T4 bacteriophage is an example.

PrionsPrions are pathogenic, virus-like particles made up completely of misfolded proteins. They are not made up of DNA or RNA.

PrionsExampleMad Cow Disease (bovine spongiform encephalopathy)Most prions affect the structure of the brain or other neural tissue, and all are currently untreatable and are always fatal.

ViroidsA viroid is a plant pathogen that consists of a short stretch of RNA. Potato Spindle Tuber Viroid

ViroidsA viroid is a plant pathogen that consists of a short stretch of RNA.

Put It All Together!Write down 3 things you have learned about viruses.