viruses living or not ???????. viruses virus – latin for “_poison__” virus – latin for...

VirusesVirusesLiving or NotLiving or Not

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VirusesViruses Virus – Latin for “_Poison__”Virus – Latin for “_Poison__” TMV - 1930TMV - 1930

Characteristics of Characteristics of VirusesViruses

Science of Viruses – Virology!Science of Viruses – Virology!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!

Studying the “T4-Studying the “T4-BacteriophageBacteriophage

Also known as:Also known as: “eaters of bacteria” “eaters of bacteria” have a head and tail region – (serve have a head and tail region – (serve as the principle experimental object as the principle experimental object in studying viruses)in studying viruses)

Check out: http://www.cellsalive.com/phage.htm

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!

What are Viruses Made What are Viruses Made of?of?

Viruses are composed of nucleic acid, proteins, and Viruses are composed of nucleic acid, proteins, and sometimes, lipids. They are not very sometimes, lipids. They are not very complexcomplex!!

The Nucleic acid core, which can be either The Nucleic acid core, which can be either DNADNA or or RNARNA, encodes the genetic information to make virus , encodes the genetic information to make virus copies.copies.

The nucleic acid is surrounded by a protective The nucleic acid is surrounded by a protective protein coat, called a capsid. These are called protein coat, called a capsid. These are called ““nakednaked” viruses.” viruses.

An outer membranous layer, called an envelope, An outer membranous layer, called an envelope, made of lipid and protein, surrounds the capsid in made of lipid and protein, surrounds the capsid in some viruses…..these ones are called some viruses…..these ones are called “enveloped “enveloped viruses”viruses”

The capsid accounts for 95% of the total virus, The capsid accounts for 95% of the total virus, and gives the virus a particular shapeand gives the virus a particular shape

Virus StructureVirus Structure

Nucleic acid

Envelope

Capsid

How are Viruses How are Viruses Classified?Classified?

Genetic MaterialGenetic Material DNA orDNA or RNARNA But not bothBut not both

Capsid StructureCapsid Structure Helical (rod shaped)Helical (rod shaped) Polyhedral (spherical)Polyhedral (spherical) ComplexComplex

Presence or absencePresence or absence of a membranousof a membranous envelope envelope surrounding surrounding the capsidthe capsid

Helical Marburg virus

Polyhedral SV40 virus

Complex bacteriophage

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

Mem. e.Organelles - no Psotn yes yes yes yes.o

History of VirusesHistory of Viruses

Invasions, wars, and immigrationInvasions, wars, and immigration can can introduce viral diseases to different introduce viral diseases to different populations populations

Some viral infections have had major Some viral infections have had major global effects:global effects: Influenza type A is believed to be responsible Influenza type A is believed to be responsible

for global flu outbreaks in for global flu outbreaks in 1918, 1957 and 1918, 1957 and 19681968

16th century Spanish explorers brought 16th century Spanish explorers brought small small pox, measles and influenza virusespox, measles and influenza viruses to the to the New WorldNew World

Viruses - DiseaseViruses - Disease

Viral infections generally behave Viral infections generally behave in 2 ways:in 2 ways:

1. Viruses reproduce and cause 1. Viruses reproduce and cause disease immediately (disease immediately (lytic or lytic or activeactive))

2. Viruses integrate into the host cell 2. Viruses integrate into the host cell ((lysogenic or dormant)lysogenic or dormant)

Viral Replication – Lytic Viral Replication – Lytic Cycle InfectionCycle Infection

See clip on desktop!!

LYSOGENIC CYCLE

See clip on desktop!!!

Viral Replication – Viral Replication – Lysogenic Cycle Infection Lysogenic Cycle Infection

The host cell makes copies of the virus The host cell makes copies of the virus indefinitely indefinitely

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

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

The viral DNA embedded in the host’s DNA is The viral DNA embedded in the host’s DNA is called a called a prophageprophage and it can remain in the and it can remain in the host cell for many… generations before host cell for many… generations before becoming becoming activatedactivated

What organisms and Host What organisms and Host cells do Viruses Infect?cells do Viruses Infect?

INFECTION BY A VIRUS:INFECTION BY A VIRUS: Viruses infect bacteria, plants, animals and Viruses infect bacteria, plants, animals and

other living organisms in order to reproduce.other living organisms in order to reproduce. Narrow host range. Ex: smallpox is only Narrow host range. Ex: smallpox is only

capable of infecting humans and no other capable of infecting humans and no other species.species.

Viruses are cell specific. Ex: viruses that cause Viruses are cell specific. Ex: viruses that cause respiratory disease usually infect cells only in respiratory disease usually infect cells only in the respiratory tract.the respiratory tract.

Determined by a lock-and-key fit between the Determined by a lock-and-key fit between the virus and the receptor (proteins) on the virus and the receptor (proteins) on the surface of a host cell.surface of a host cell.

•HIV, for example, only will enter cells that have a surface protein molecule called CD4. These molecules are found only on white blood cells. Thus, HIV will only infect white blood cells and not lung cells or other cell types. •Sometimes, a virus can mutate and change its host range. This appears to be happening with the avian flu virus (influenza A/H5N1) currently circulating. At first, the flu virus could infect only birds, but changes in the virus genome have allowed it to infect humans. So now, its host range has expanded. The change in host range of a virus can be one factor in the emergence of a new disease.

Host RangeHost Range

What Diseases are Caused What Diseases are Caused by Viruses?by Viruses?

Infectious diseasesInfectious diseases RNA virusesRNA viruses (retroviruses) (retroviruses) DNA virusesDNA viruses

AIDSAIDS Respiratory DiseaseRespiratory Disease

Influenza (flu) Influenza (flu) SmallpoxSmallpox

Common coldCommon cold ChickenpoxChickenpox

PolioPolio MononucleosisMononucleosis

MeaslesMeasles Cold SoresCold Sores

Tumor Viruses – cause Cancer ex: HPVTumor Viruses – cause Cancer ex: HPV

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 Avoid contact with contaminated food, water, fecal

material or body fluids.material or body 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 Contain a component of or a weakened or killed virus

particles.particles. Are developed for many once common illnesses such as Are developed for many once common illnesses such as

smallpox, polio, mumps, chicken pox.smallpox, polio, 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. Inhibit some virus development and/or relieve Inhibit some virus development and/or relieve

symptoms.symptoms.

How Do New Viruses How Do New Viruses Emerge?Emerge?

Through mutation and evolutionThrough mutation and evolution By spreading from one species to a By spreading from one species to a

new host speciesnew host species By spreading from an isolated By spreading from an isolated

location to more widespread location to more widespread locationslocations

Through the detection of previously Through the detection of previously unrecognized virusesunrecognized viruses

HSV1 vs HSV2

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

HPV virus – genital wartsHPV virus – genital warts

Polio VirusPolio Virus

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

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. IN ORDER FOR A VIRUS TO 3. IN ORDER FOR A VIRUS TO REPLICATE IT NEEDS TO BE REPLICATE IT NEEDS TO BE IN A 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. ANOTHER NAME FOR 6. 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. 3 WAYS THAT VIRUSES CAN 3 WAYS THAT VIRUSES CAN BE TRANSMITTED ARE….BE TRANSMITTED ARE….

-- droplets in the air (e.g. cold, flu, tuberculosis)-- via food or water (e.g. Salmonella, food

poisoning)-- via mosquitoes, ticks (e.g. malaria, West Nile

virus, Lyme disease)-- physical contact (e.g. pinkeye, herpes,

chickenpox, sexually transmitted diseases)


10. A VIRUS THAT HAS ONLY A 10. 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 living or not ???????. viruses virus – latin for “_poison__” virus – latin for...

Documents

viruses virus latin

enveloped viruses

influenza viruses

naked viruses

studies viruses

virus copies

total virus

virions virus particles