VIRUS NOTES Name: ____________________ Per: ___IMPORTANT TERMS

1. __________—an organism that shelters and nourishes something.2. ________________—an RNA virus that replicates by first transcribing(copying) RNA into DNA instead of

DNA to RNA. (ex. HIV)3. _____________--a substance produced from “killed” or weakened pathogens or inactivated toxins.

Viruses can help prevent viruses. Antibiotics _________ destroy viruses. A vaccine works by _____________ the virus from attaching to cells in your body or by attacking and _____________ specific enzymes.

4. ____________—the protein coat of a virus.5. ________________ —a viral DNA segment inserted into a bacterial cell6. ____________—the breaking apart of the cell to release new viruses.7. _______________—a virus that attacks a bacteria.

DISCOVERY OF VIRUSESNear the end of the 19th century, scientists were trying to find a cause of tobacco mosaic disease, which stunts the growth of tobacco plants. In 1897, scientists filtered tiny particles from the sap of infected plants and found that the filtered sap could cause uninfected plants to become infected..........Scientists named the tiny particles in the sap viruses, after the Latin word for poison.In 1935, the American biochemist Wendell Stanley purified the tobacco mosaic virus (TMV) and crystallized it. Living organisms don’t crystallize so Stanley concluded that the TMV was non-living and a chemical.

CHARACTERISTICS OF VIRUSES1. They are _________________ particles.2. They are segments of ____________________ surrounded by a protein coat.3. Viruses are NOT cells and are __________ than prokaryotes.4. Viruses are considered ___________________ - agents causing disease.

VIRUSES: NONLIVING OR LIVING? Not normally classified (not in Domain, Kingdom, etc.; no genus species name). Viruses are generally considered to be __________________ because they

o Can only reproduce inside of ________________o Do not have a ____________________o Do not maintain __________________________o Do not __________

Viruses are Similar to Living Cells in that they

o Have genetic material (______ or ______)

o Have ________________o Have receptor/marker

molecules on the outside for

communication/recognitiono Change over time (mutate/evolve)

STRUCTURE OF A VIRUS2 Parts: 1. Core of _______________ ________ on the inside

Nucleic acid is either _______ or _______ 2. _______________ ___________

Protein coat is called the _____________ which surrounds the nucleic acid on outside

FIVE BASIC SHAPES OF VIRUSES (draw an example of each below next to the description, label the capsid and the nucleic acid)

1. HELICAL2. SPHERICAL

3. POLYHEDRAL4. BINAL

5. FILOVIRUS

HELICAL____________in appearance with capsid proteins winding around a core of either DNA or RNAEx: tobacco mosaic virus (TMV)

SPHERICALTypically studded with _____________ which help the virus enter the cell May be ______________ (membrane around capsid)Ex: _______________ (flu virus)

POLYHEDRAL VIRUSHas many sides and is ______________ in appearanceEx: ________________ (causes the common cold)

BINAL________________ __________ containing either DNA orRNAHelical tail “fibers:Ex:_________________ (virus infecting a bacteria)

FILOVIRUSLong rods that form filaments with NO distinct shapeEx. _____________________ viruses - many are emergent viruses —viruses that humans have suddenly contracted such

as West Nile Virus and Hantavirus

SURFACE MARKER/RECEPTOR PROTEINS Virus surface proteins are very _____________ - attach to cell surface

proteins much like pieces of a puzzle fit together. This facilitatestheir ________ across the cell membrane

VIRAL FUNCTIONDISEASES CAUSED BY VIRUSES

Adenovirus (common cold) AIDS Avian Bird Flu Chicken pox (varicella)* Ebola HPV *

Rotavirus*

Hepatitis ABC Influenza (Flu)* Mumps* Polio*

Rabies* Rubella (German measles)* SARS Small pox (variola) Warts West Nile

*Routinely immunized against

Helical Virus

Spherical Virus

Binal Virus Filovirus

Polyhedral Virus

NO viral diseases are treatable with antibiotics!!!! Antibiotics are used to treat bacterial infections ONLY. Vaccines can be used to prevent getting some viruses.

VIRAL REPLICATION Viruses replicate inside _____________ ____________ They enter a cell by injecting their _____________ material into the cell

__________ in the plant cell wall binds to molecules on the cell surface and triggers __________________

RETROVIRUS Viruses that get their genetic information copied backwards……

From RNA to DNA (instead of DNA to RNA) Ex: HIV (Human Immunodeficiency Virus)—causes the disease AIDS

o contains RNA & inject it into host cello When the virus infects the cell, they produce a DNA copy of their RNA. The retrovirus

may remain _____________for varying lengths of time before becoming active, producing new viruses and then causing the death of the host cell.

2 CYCLES FOR VIRAL REPRODUCTION: 1. ___________________ & 2. ______________________

LYTIC CYCLE Characterized by viral ____________, ___________________, and cell ____________________

Virus enters cell, often just the genetic material is injected Example: Bacteriophage T4 – has DNA core inside a protein capsid that binds to the

surface of a host cell. Virus injects its DNA into the cell and the cell begins to make mRNA from the viral genes. The viral mRNA is translated into viral proteins that act like a “molecular wrecking crew”, chopping up the cell’s DNA

Under the control of the viral genes (_____________), host cell now makes ________ of viral ___________________ and capsid _____________.

Viral nucleic acid is assembled into new virus particles Soon the host cell is full of new viruses that _________ (lyse) from the cell, spreading the

virus particles and disease Host cell now _____________

LYTIC CYCLE SUMMARY1. Virus attaches to host2. Virus enters cell (nucleic acid is injected)3. Replicates immediately4. Produces many new viruses

5. Viruses burst from cell to invade other cells (this is the step that harms or kills the cell)

LYSOGENIC CYCLE The viral ___________ (DNA) replicates without destroying the host cell Virus inserts its DNA into the host’s DNA and it “hides” there - becomes a ______________ Host cell reproduces as usual (making more viral DNA without knowing it!!!!). The host cell is

not harmed. Later it will begin the __________ cycle to spread the virus. There is usually a change in the

environment (heat or chemicals) that causes the provirus to begin the lytic cycle. This will then result in the destruction of the host cell.

LYSOGENIC CYCLE SUMMARY 1. Virus invades cell2. Does not immediately kill host cell3. Becomes part of the host’s DNA4. Host cell reproduces as usual (making more viral DNA without knowing it)5. Eventually goes into the lytic cycle to spread the virus

VIRAL REPRODUCTION CYCLES

HUMAN IMMUNODEFICIENCY VIRUS is a retrovirus since it contains RNA, not DNAHIV, the virus that can result in the disease AIDS, can hide for years in the nucleus of ___________ (white blood cells that help fight infection) in the_________________. People can have no symptoms, yet be spreading the disease to many partners. HIV then begins the _______________and T-cells begin to die. HIV infection leads to the destruction of the body’s T cells and weakens the immune system. This can lead to AIDS (when T cell count is below 200 cells/ml)The patient eventually dies from another disease (opportunistic infection) that the immune system can’t control because there are not enough T-cells to help fight infection

Structure of HIVo Exterior Viral envelope studded with

glycoproteins which precisely fits a human cell surface receptor

o Inside the envelope is the capsid; and inside the capsid are 2 molecules of RNA

VIRUSES AND CANCERMany cancers can result from viral infectionsHOW? Because when a virus infects a cell it can cause ___________ in the cell to turn on or off. This can interrupt the _________ _____________, causing the cell to divide ________________. Remember that this is _____________!Ex: _________ – this virus can infect women and result in cervical cancer; there’s a vaccine for itEx: _________________ – can often lead to liver cancer

AIDS and cancer, as well as many common infections (colds, influenza, & warts), are caused by viruses. So are many more severe (but rarer in the U.S.) infections.

Disease Description How transmitted Nucleic Acid

AIDSImmune system failure Sexual contact, blood, needles, breast milk

RNA

Avian Bird FluBegins as Influenza, sever cases develop pneumonia

Bird droppings, salivaRNA

ChickenpoxHeadache, fever, rash, itchy vesicles containing clear fluid

Inhalation of droplets form the nose or throatDNA

Common ColdSinus congestion, muscle aches, cough, fever

Inhalation, direct contactDNA

EbolaHigh fever, uncontrollable bleeding Body fluids

RNA

Hepatitis AFlulike symptoms, swollen liver, yellow skin, painful joints

Contaminated blood, food, or waterDNA

Hepatitis BFlu-like symptoms, swollen liver, yellow skin, painful joints, and can cause liver cancer

Sexual contact, contaminated blood, or needles DNA

InfluenzaFever, chills, fatigue, cough, sore throat, muscle aches, weakness, headaches

InhalationRNA

MumpsPainful swelling in salivary glands Inhalation

RNA

PolioFever, headache, stiff neck, possible paralysis

Contaminated food or waterRNA

RabiesMental depression, fever, restlessness, difficulty swallowing , paralysis, convulsion,

Bite of infected animalRNA

can be fatal

SARSAcute respiratory disorder, high fever, body aches, chills, diarrhea, cough, 2-7 days incubation

Close person to person contact, Inhalation, respiratory droplets from a cough or sneeze RNA

West NileHeadache, pain behind the eyes, neck stiffness, fever, cough, vomiting, jaundice, and scarlet fever-type rash. More serious signs are confusion and high fever. Invades liver, nerve, and brain

Mosquitoes are the host RNA