Viruses Living or Not ???????. Viruses Virus – Latin for “_Poison__” Virus – Latin for...
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Transcript of 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
MINI QUIZ…MINI QUIZ…
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
MINI QUIZ…MINI QUIZ…
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!
MINI QUIZ…MINI QUIZ…
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
MINI QUIZ…MINI QUIZ…
6. ANOTHER NAME FOR 6. ANOTHER NAME FOR INFLUENZA IS INFLUENZA IS FLU VIRUSFLU VIRUS
MINI QUIZ…MINI QUIZ…
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
MINI QUIZ…MINI QUIZ…
8. SCIENTISTS THAT STUDY 8. SCIENTISTS THAT STUDY VIRUSES ARE CALLED VIRUSES ARE CALLED VIROLOGISTSVIROLOGISTS
MINI QUIZ…MINI QUIZ…
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)
MINI QUIZ…MINI QUIZ…
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.