viruses viruses are insidious pathogens, they attack cells from the inside. they hijack your own dna...

VirusesVirusesViruses are insidious pathogens, they attack cells from the Viruses are insidious pathogens, they attack cells from the inside. They hijack your own DNA and use it against you. inside. They hijack your own DNA and use it against you. A virus cannot be treated with antibiotics, it can only run A virus cannot be treated with antibiotics, it can only run its course until your immune system kicks it out.its course until your immune system kicks it out.

..Even then, the virus may lay dormant within the cells and ..Even then, the virus may lay dormant within the cells and come back at a later datecome back at a later date

Adenovirus - cause of the common cold

VirusesViruses Virus – Latin for “_Poison__”Virus – Latin for “_Poison__” Russian Biologist Dmitri Ivanovski Russian Biologist Dmitri Ivanovski

(1892) – Tobacco Mosaic Disease…(1892) – Tobacco Mosaic Disease…not determined to be a virus until not determined to be a virus until 1930…known as the first virus to be 1930…known as the first virus to be discovered!~discovered!~

Characteristics of Characteristics of VirusesViruses

Scientist that studies viruses is called a Scientist that studies viruses is called a virologist!virologist! Among the Among the

smallest smallest biological biological particlesparticles (not cells) (not cells) that are capable of that are capable of causing harm in causing harm in living organisms. living organisms.

Virus particles are Virus particles are called called virionsvirions

5000 influenza 5000 influenza viruses can fit viruses can fit inside the head of a inside the head of a pin!pin!

Properties of a Virus:Properties of a Virus:•no membranes, cytoplasm, ribosomes, or other cellular no membranes, cytoplasm, ribosomes, or other cellular componentscomponents•they cannot move or growthey cannot move or grow•they can only reproduce inside a host cellthey can only reproduce inside a host cell•they consist of 2 major parts - a protein coat, and hereditary they consist of 2 major parts - a protein coat, and hereditary material (DNA or RNA)material (DNA or RNA)•they are extremely tiny, much smaller than a cell and only they are extremely tiny, much smaller than a cell and only visible with advanced electron microscopesvisible with advanced electron microscopes

VIRUSES & CELLSVIRUSES & CELLSCharacteristicCharacteristic VIRUSVIRUS CELLCELL

StructureStructure DNA or RNA core, DNA or RNA core, capsidcapsid

ReproductionReproduction Only within a hostOnly within a host

Genetic CodeGenetic Code DNA or RNADNA or RNA

Growth/DvpmtGrowth/Dvpmt NONO

EnergyEnergy NONO

Response to Response to EnvironmentEnvironment

NoNo

Change over timeChange over time YesYes

Not Considered LivingNot Considered Living

A virus is not a A virus is not a bacteria, fungus, bacteria, fungus, protist, plant or animal.protist, plant or animal.

They They do not carry out do not carry out cellular functionscellular functions..

They They do not grow or do not grow or undergo divisionundergo division

A virus A virus can not can not replicate on their replicate on their ownown – they need to – they need to infect a infect a HOSTHOST and use and use the hosts organelles the hosts organelles and enzymes to do this!and enzymes to do this!

How Are Viruses Named?1. Nature of the nucleic acid (DNA or RNA)2. Protein shell and symmetry3. Geographic Origin4. Year of Isolation5. Named after the infected species (Swine Flu, Avian Flu..)6. Named after a person (either a patient or a doctor)

Example of an Influenza Virus

How are Viruses How are Viruses Classified?Classified?

1. Genetic Material1. Genetic Material DNA orDNA or RNA RNA

(retrovirus/mutates (retrovirus/mutates frequently)frequently)

But not bothBut not both2. Capsid (Protein) 2. Capsid (Protein) Structure (95% of virus)Structure (95% of virus)

Helical (rod shaped)Helical (rod shaped) Polyhedral (spherical)Polyhedral (spherical) ComplexComplex

3. Presence or absence3. Presence or absence of of a membranousa membranous envelope envelope surrounding the capsidsurrounding the capsid**No envelope = naked virus**No envelope = naked virus

Helical Marburg virus

Polyhedral SV40 virus

Complex bacteriophage

Virus Structure

Parasitic Nature Parasitic Nature ObligateObligate intracellular parasites (they cannot exist independently) intracellular parasites (they cannot exist independently)

Specific to hostsSpecific to hosts (human, dog, some can cross species) (human, dog, some can cross species)

Specific to cellsSpecific to cells , the common cold is a virus that specifically , the common cold is a virus that specifically attacks cells of the respiratory track (hence the coughing and attacks cells of the respiratory track (hence the coughing and sneezing and sniffling). HIV specifically attacks white blood sneezing and sniffling). HIV specifically attacks white blood cellscells

This is a bacteriophage, a type of virus that attacks bacteria. It is recognizeable because it looks like the lunar landing spaceship.**Most widely studied virus!!!See animation http://www.youtube.com/watch?v=41aqxcxsX2w&feature=related

Viral Reproduction Viral Reproduction

Lytic cycle = ACTIVE…reproduction occurs, cells burstLytic cycle = ACTIVE…reproduction occurs, cells burstLysogenic cycle = DORMANT…reproduction does not Lysogenic cycle = DORMANT…reproduction does not immediately occur immediately occur

Virulent = viruses that undergo both cyclesVirulent = viruses that undergo both cycles

Viral Replication – Lytic Viral Replication – Lytic Cycle InfectionCycle Infection

See clip on desktop!!

Lytic (kills cells dead)Lytic (kills cells dead) AdsorptionAdsorption – (aka attachment) chemical attraction – (aka attachment) chemical attraction

between the tail fibers and receptor proteins on the between the tail fibers and receptor proteins on the host cell (lock & key fit)host cell (lock & key fit)

EntryEntry – release an enzyme to weaken the wall of – release an enzyme to weaken the wall of bacterium & tail sheath contracts forcing a tube in. bacterium & tail sheath contracts forcing a tube in. (like a needle)(like a needle)

ReplicationReplication – enzymes degrate host DNA and – enzymes degrate host DNA and stops making its molecules and begins using the stops making its molecules and begins using the viruses genome to make copiesviruses genome to make copies

AssemblyAssembly – proteins spontaneously attach together – proteins spontaneously attach together ReleaseRelease - The newly assembled viruses are - The newly assembled viruses are

released from the host bacterial cell as the enzyme released from the host bacterial cell as the enzyme completes its degradation of the cell wall and the completes its degradation of the cell wall and the bacteria disintegrates.bacteria disintegrates.

LYSOGENIC CYCLE

See clip on desktop!!!

Viral Replication – Viral Replication – Lysogenic Cycle InfectionLysogenic Cycle Infection The host cell makes copies of the virus The host cell makes copies of the virus

indefinatelyindefinately The virus integrates its DNA into the DNA of The virus integrates its DNA into the DNA of

the host cell, and the viral genetic the host cell, and the viral genetic information replicates along with the host information replicates along with the host cell’s DNA.cell’s DNA.

Unlike lytic viruses, lysogenic viruses DO Unlike lytic viruses, lysogenic viruses DO NOT lyse the host cell right away. (it can NOT lyse the host cell right away. (it can remain inactive for a long period of time)remain inactive for a long period of time)

The viral DNA embedded in the host’s DNA The viral DNA embedded in the host’s DNA is called a is called a prophageprophage and it can remain in and it can remain in the host for many years before becoming the host for many years before becoming active.active.

What Organisms and Host What Organisms and Host Cells Do Viruses Infect?Cells Do Viruses Infect?

Infection by virusesInfection by viruses viruses infect bacteria, plants, animals and other living viruses infect bacteria, plants, animals and other living

organisms in order to reproduceorganisms in order to reproduce a given virus usually infects a limited number of a given virus usually infects a limited number of

species.species. within a host organism, usually only a limited number of within a host organism, usually only a limited number of

cell types are susceptible to infection by a given viruscell types are susceptible to infection by a given virus Host rangeHost range

array of host cells that a particular virus can infect array of host cells that a particular virus can infect determined by a “lock-and-key” fit between the virus determined by a “lock-and-key” fit between the virus

and a receptor on the surface of a host cell proteinand a receptor on the surface of a host cell protein Ex: Ex: HIVHIV, for example, only will enter cells that have a , for example, only will enter cells that have a

surface protein molecule called CD4surface protein molecule called CD4. These . These molecules are found only on molecules are found only on white blood cellswhite blood cells. Thus, . Thus, HIV will only infect white blood cells and not lung HIV will only infect white blood cells and not lung cells or other cell typescells or other cell types. .

Emerging Viruses: Emerging Viruses:

illnesses not previously knownillnesses not previously known

AIDS, West Nile Virus, SARS, Ebola, Bird Flu AIDS, West Nile Virus, SARS, Ebola, Bird Flu

• Could be genetic code mutations of known viruses…protein coat changes that Could be genetic code mutations of known viruses…protein coat changes that are unrecognizable to host’s immune systemare unrecognizable to host’s immune system

• Could be viruses exposed when new areas were developed Could be viruses exposed when new areas were developed • Could have jumped species (avian flu, swine flu)Could have jumped species (avian flu, swine flu)

How do our bodies fight How do our bodies fight viruses?viruses? Functions of the Immune System:Functions of the Immune System:

Recognition:Recognition: Antibodies (proteins that bind to the surface of Antibodies (proteins that bind to the surface of

a virus) recognize an infected cell and attach.a virus) recognize an infected cell and attach.

Destruction:Destruction: Leukocytes move in to destroy the infected Leukocytes move in to destroy the infected

cellscells Also known as White Blood Cells that come Also known as White Blood Cells that come

from the bone marrowfrom the bone marrow Goal is to recognize foreign substances (not Goal is to recognize foreign substances (not

healthy cells)healthy cells)

Memory: Memory: Once infected, memory cells recognize the Once infected, memory cells recognize the

virus if it enters the cell again!virus if it enters the cell again!

How Can Viral Diseases Be How Can Viral Diseases Be Prevented and Treated?Prevented and Treated?

Good hygieneGood hygiene Avoid contact with contaminated food, water, fecal material or body Avoid contact with contaminated food, water, fecal material or body

fluids.fluids. Wash hands frequently.Wash hands frequently.

VaccinesVaccines Stimulate natural defenses with in the body.Stimulate natural defenses with in the body. Contain a component of or a weakened or killed virus particles.Contain a component of or a weakened or killed virus particles. Are developed for many once common illnesses such as smallpox, polio, Are developed for many once common illnesses such as smallpox, polio,

mumps, chicken pox.mumps, chicken pox. Not available for all viruses.Not available for all viruses.

Anti-viral drugs (but not antibiotics)Anti-viral drugs (but not antibiotics) Available for only a few viruses.Available for only a few viruses. There are two FDA-approved antiviral drugs recommended by CDC. The There are two FDA-approved antiviral drugs recommended by CDC. The

brand names for these are Tamiflu® (generic name oseltamivir) and brand names for these are Tamiflu® (generic name oseltamivir) and Relenza® (generic name zanamivir).Relenza® (generic name zanamivir).

Used to relieve symptomsUsed to relieve symptoms Other antivirals block the viruses at various stages of their life cycle, such Other antivirals block the viruses at various stages of their life cycle, such

as blocking cell receptors, preventing attachment or preventing viral as blocking cell receptors, preventing attachment or preventing viral repication after the virus has entered the cell. repication after the virus has entered the cell.

Some parents are opting out of immunizations due to fears about vaccine safety.

In response, government agencies are producing commercials to encourage parents to get their child vaccinated.

Discuss:

1. What are the risks of vaccines? Are they safe?2. Would you have your own child vaccinated?3. Should the government force immunizations?

RV = rotovirus; DTaP = diptheria, tetanus, pertussis (whooping cough); Hib = RV = rotovirus; DTaP = diptheria, tetanus, pertussis (whooping cough); Hib = haemophilus influenza type B; PCV = pneumococcal vaccine; IPV = haemophilus influenza type B; PCV = pneumococcal vaccine; IPV = inactivated polio virus; MMR = measles, mumps, rubella, inactivated polio virus; MMR = measles, mumps, rubella,

Retroviruses -- RNA viruses that have a DNA stage Retroviruses -- RNA viruses that have a DNA stage • Human Immunodefiency Virus - causes AIDS Human Immunodefiency Virus - causes AIDS • Retrovirus (RNA inside a protein coat) Retrovirus (RNA inside a protein coat) • Reverse Transcriptase makes DNA from the virus RNA Reverse Transcriptase makes DNA from the virus RNA • DNA inserts into host DNA DNA inserts into host DNA • Proteins are assembled from the DNA code Proteins are assembled from the DNA code • Viruses assembled from the proteins Viruses assembled from the proteins • Viruses released from the cellViruses released from the cell

(Link) HIV Animation - how virus infects cells

What we know about HIV.....What we know about HIV.....

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.

HSV1 vs HSV2

Human Papilloma Virus – Human Papilloma Virus – 14yo boy14yo boy

http://www.youtube.com/watch?v=6E1zh6ukcOU

Polio VirusPolio Virus

Six countries (Afghanistan, Egypt, India, Niger, Nigeria, and Pakistan) still have polio circulating

Now Let’s Check Now Let’s Check Your Knowledge!!Your Knowledge!!

Mini Virus QuizMini Virus Quiz

VIRUS MINI QUIZVIRUS MINI QUIZ

1.1. THE PRIMARY FUNCTION THE PRIMARY FUNCTION OF ALL VIRUSES IS TO OF ALL VIRUSES IS TO

REPLICATE!!REPLICATE!!

MINI QUIZ…MINI QUIZ…

2. 2. WHAT IS THE WHAT IS THE TYPICAL/COMMON VIRUS TYPICAL/COMMON VIRUS THAT STUDENTS STUDY THAT STUDENTS STUDY WHEN LEARNING ABOUT WHEN LEARNING ABOUT VIRUSES?VIRUSES?

T4 BacteriophageT4 Bacteriophage


3.3. IN ORDER FOR A VIRUS TO IN ORDER FOR A VIRUS TO REPLICATE IT NEEDS TO REPLICATE IT NEEDS TO BE IN A…. BE IN A….

HOSTHOST CELL CELL


4. VIRAL REPRODUCTION 4. VIRAL REPRODUCTION THAT KILLS THE HOST CELL THAT KILLS THE HOST CELL IS CALLED THE IS CALLED THE

LyticLytic CYCLE! CYCLE!


5. WHEN VIRAL DNA IS 5. WHEN VIRAL DNA IS EMBEDDED INTO A HOST EMBEDDED INTO A HOST CELL’S DNA IT FORMS A….CELL’S DNA IT FORMS A….

PROPHAGEPROPHAGE


6.6. ANOTHER NAME FOR ANOTHER NAME FOR INFLUENZA IS….INFLUENZA IS….

FLU VIRUSFLU VIRUS


7. 3 WAYS VIRUSES CAN BE 7. 3 WAYS VIRUSES CAN BE TREATED/PREVENTED TREATED/PREVENTED ARE….ARE….

1.1. HygieneHygiene

2.2. VaccinesVaccines

3.3. AntiViralsAntiVirals


8. SCIENTISTS THAT STUDY 8. SCIENTISTS THAT STUDY VIRUSES ARE CALLED VIRUSES ARE CALLED VIROLOGISTSVIROLOGISTS


9.9. 2 WAYS THAT VIRUSES 2 WAYS THAT VIRUSES CAN BE TRANSMITTED CAN BE TRANSMITTED ARE….ARE….

-- droplets in the air -- via food or water

-- via mosquitoes, ticks other animals-- physical contact


10.10. A VIRUS THAT HAS ONLY A A VIRUS THAT HAS ONLY A CAPSIDCAPSID SURROUNDING IT’S SURROUNDING IT’S GENETIC INFORMATION AND GENETIC INFORMATION AND NO NO ENVELOPEENVELOPE IS CALLED A…. IS CALLED A….

NAKEDNAKED VIRUS. VIRUS.

viruses viruses are insidious pathogens, they attack cells from the inside. they hijack your own dna...

Documents

virus particles

type of virus

livinga virus

divisiona virus

studies viruses

virions5000 influenza

reproduction lytic cycle

lysogenic cycle