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Virus Chapter No 5 Class XI

According To The New Sallybus of Sindh Text Book Board Jamshoro

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Virus Chapter No 5 Class XI

  1. 1. Sajjad Hussain MiraniSajjad Hussain Mirani Sindh University JamshoroSindh University Jamshoro www.shm.usa.ccwww.shm.usa.cc
  2. 2. Introduction To VirusIntroduction To Virus Virus is a Latin wordVirus is a Latin word venomevenome which means poison.which means poison. Poisons which is carried through winds to various parts.Poisons which is carried through winds to various parts. Virus was 1Virus was 1stst reported in 1892 A.D. by a Russian biologistreported in 1892 A.D. by a Russian biologist Iwanowsky,Iwanowsky, he stated that virus can spread from onehe stated that virus can spread from one organism to another organism and from one person toorganism to another organism and from one person to another person.another person. There are many diseases which is considered to be caused byThere are many diseases which is considered to be caused by filterable viruses.filterable viruses. Virus was discovered by an American microbiologistVirus was discovered by an American microbiologist WendellWendell StanleyStanley in 1935 A.D after invention of electronin 1935 A.D after invention of electron microscope.
  3. 3. Viral CharacteristicsViral Characteristics Viruses areViruses are non cellularnon cellular particles and all viruses areparticles and all viruses are obligatory parasitesobligatory parasites.. Viruses lack necessary mechanism to replicate theirViruses lack necessary mechanism to replicate their genetic material outside the host cell so they cant livegenetic material outside the host cell so they cant live outside the host cell.outside the host cell. Adhesion properties of virus depends upon their proteinAdhesion properties of virus depends upon their protein biochemistry and envelop biochemistry.biochemistry and envelop biochemistry. Size of Virus varies from 20 to 250 nm in size.Size of Virus varies from 20 to 250 nm in size.
  4. 4. Virulent And Temperate VirusesVirulent And Temperate Viruses Viruses which destroy host cell after beingViruses which destroy host cell after being replicated in host cells, are known asreplicated in host cells, are known as virulent virusesvirulent viruses.. Viruses which do no destroy host cell andViruses which do no destroy host cell and live in harmony with their host fromlive in harmony with their host from generation to generation then it is knowngeneration to generation then it is known asas temperate virustemperate virus..
  5. 5. Structure Of VirusStructure Of Virus 1.1. Viral ShapesViral Shapes Viruses are of many shapes e.g. of little sphere shaped, golf ball like, tadpoleViruses are of many shapes e.g. of little sphere shaped, golf ball like, tadpole like, rod shaped or polyhedral in shape.like, rod shaped or polyhedral in shape. Usually viruses are helicular (rod / thread shape) or isometric (roughlyUsually viruses are helicular (rod / thread shape) or isometric (roughly sphericle).sphericle). 2.2. Viral Genetic MaterialViral Genetic Material Simple viruses contain single molecule ofSimple viruses contain single molecule of nucleic acidnucleic acid either DNA or RNAeither DNA or RNA while complex viruses contain several molecules of nucleic acids.while complex viruses contain several molecules of nucleic acids. 3.3. Viral CapsidViral Capsid It is a protein coat which encloses the viral genetic material.It is a protein coat which encloses the viral genetic material. Capsid is made up of monomers calledCapsid is made up of monomers called capsomerscapsomers.. Number of capsomers is a characteristic feature of different viruses.Number of capsomers is a characteristic feature of different viruses.
  6. 6. 4.4. Viral EnvelopViral Envelop In some viruses Capsid is enclosed by another layer ofIn some viruses Capsid is enclosed by another layer of protein called envelop.protein called envelop. Envelops usually increases the infectivity of virus.Envelops usually increases the infectivity of virus. Also contain lipid in their structure.Also contain lipid in their structure. 5.5. Tail FibersTail Fibers Few viruses like bacteriophage viruses contain tail plateFew viruses like bacteriophage viruses contain tail plate with tail fibers.with tail fibers. Tail fibers help virus to attach on the surface of theirTail fibers help virus to attach on the surface of their host.host.
  7. 7. Classification Of VirusClassification Of Virus Viruses are usually classified on the basisViruses are usually classified on the basis of following features.of following features. 1.1. On The Basis Of Their Genetic MaterialOn The Basis Of Their Genetic Material Viruses can be classified on the basis of theirViruses can be classified on the basis of their genetic material into following classes,genetic material into following classes, DNA virusDNA virus Have DNA as their genetic material.Have DNA as their genetic material. RNA virusRNA virus Have RNA as their genetic material.Have RNA as their genetic material.
  8. 8. On The Basis Of Their MorphologyOn The Basis Of Their Morphology On the basis of their morphology viruses mayOn the basis of their morphology viruses may be of following typesbe of following types Rod SHAPED e.gRod SHAPED e.g. tobacco mosaic virus.. tobacco mosaic virus. SphericalSpherical e.g. polio virus.e.g. polio virus. Tadpole SHAPED e.gTadpole SHAPED e.g. bacteriophage virus.. bacteriophage virus.
  9. 9. On The Basis Of Diversity Name of group Nucleic Acid Example Infect 1. Un enveloped plus strand RNA virus. RNA Polio and Rhino viruses Plant, bacteria and man 2. Enveloped plus strand RNA virus. RNA Hepatitis A and C viruses Arthropods and vertebrates 3. Minus strand RNA virus. RNA Rhabdo and Pox viruses Plants and animals 4. Retroviruses RNA HIV and Hepatitis B viruses Animals 5. Double strand RNA virus. RNA Reo Viruses Plants and animals 6. Small genome DNA virus. DNA Parvo viruses Animals 7. Medium and large genome DNA virus. DNA Herpes Viruses Man 8. Bacteriophage DNA Bacteria
  10. 10. Life Cycles Of Bacteriophage VirusLife Cycles Of Bacteriophage Virus These are the various methods by whichThese are the various methods by which bacteriophage virus replicates itself to formbacteriophage virus replicates itself to form new viruses of its own kind.new viruses of its own kind. Life cycle of Bacteriophage is of two typesLife cycle of Bacteriophage is of two types
  11. 11. Lytic CycleLytic Cycle A type of life cycle which ends in to theA type of life cycle which ends in to the death of host cell.death of host cell. This type of association b/w virus andThis type of association b/w virus and bacteria is known asbacteria is known as master – slavemaster – slave relationshiprelationship as virus becomes masteras virus becomes master and bacterial cell becomes slave.and bacterial cell becomes slave. Viruses which only reproduce by lyticViruses which only reproduce by lytic cycle are known as virulent viruses.cycle are known as virulent viruses.
  12. 12. What Happened in Lytic Cycle ?What Happened in Lytic Cycle ? Phage virus stick on the surface of bacterial cell.Phage virus stick on the surface of bacterial cell. Bacteriophage then insert its DNA in to the bacterial cell byBacteriophage then insert its DNA in to the bacterial cell by contracting its tail and forming and hollow core through cellcontracting its tail and forming and hollow core through cell wall and cell membrane of bacterial cell.wall and cell membrane of bacterial cell. Viral DNA destroys DNA of bacterial cell and controls allViral DNA destroys DNA of bacterial cell and controls all activities of bacterial cell.activities of bacterial cell. Viral DNA use metabolic machinery of bacterial cell to formViral DNA use metabolic machinery of bacterial cell to form various components of virus like Capsid and nucleic acids, etc.various components of virus like Capsid and nucleic acids, etc. In the last viral DNA start forming enzymes which digestIn the last viral DNA start forming enzymes which digest bacterial cell and newly formed viruses released and attacks onbacterial cell and newly formed viruses released and attacks on new bacterial cells.new bacterial cells.
  13. 13. Lysogenic CycleLysogenic Cycle In this cycle, viral DNA replicates inside theIn this cycle, viral DNA replicates inside the bacterial cell without destroying bacterial cell.bacterial cell without destroying bacterial cell. This type of association is known asThis type of association is known as host -host - guest relationshipguest relationship b/w virus and bacteria.b/w virus and bacteria. Viruses that replicate by using Lysogenic cycleViruses that replicate by using Lysogenic cycle are known as temperate virusesare known as temperate viruses
  14. 14. What Happened In Lysogenic CycleWhat Happened In Lysogenic Cycle Bacteriophage virus attached on the surface of bacterial cell.Bacteriophage virus attached on the surface of bacterial cell. bacteriophage virus insert its DNA in bacterial cell.bacteriophage virus insert its DNA in bacterial cell. viral DNA in bacterial cell incorporated in bacterial DNA insteadviral DNA in bacterial cell incorporated in bacterial DNA instead of destroying bacterial DNA.of destroying bacterial DNA. with each successive replication of bacterial DNA, viral DNAwith each successive replication of bacterial DNA, viral DNA which is incorporated in bacterial DNA also replicated and thiswhich is incorporated in bacterial DNA also replicated and this cycle is going on and on.cycle is going on and on. Some times due to some environmental trigger, viral DNA exitsSome times due to some environmental trigger, viral DNA exits bacterial DNA and initiate lytic cycle and causing death ofbacterial DNA and initiate lytic cycle and causing death of bacterial cell.bacterial cell.
  15. 15. Transmission Of Viral DiseasesTransmission Of Viral Diseases There are several routes by which viral diseases can beThere are several routes by which viral diseases can be transferred from person to person, few important are astransferred from person to person, few important are as follows.follows. 1.1.Droplet infections e.g. flu.Droplet infections e.g. flu. 2.2.Via infectedVia infected salivasaliva e.g. AIDS.e.g. AIDS. 3.3.Via infected feces e.g. hepatitis A and E.Via infected feces e.g. hepatitis A and E. 4.4.Via sexual intercourse e.g. AIDS and hepatitis B & C.Via sexual intercourse e.g. AIDS and hepatitis B & C. 5.5.Via wounds in skin e.g. Rabies and AIDS.Via wounds in skin e.g. Rabies and AIDS.
  16. 16. Viral Diseases In AnimalsViral Diseases In Animals PoliomyelitisPoliomyelitis Caused byCaused by polio viruspolio virus.. Disease of motor neurons present in anterior horn cells of spinalDisease of motor neurons present in anterior horn cells of spinal cord.cord. Largely under control by the development ofLargely under control by the development of polio vaccinepolio vaccine.. ColdsColds Upper respiratory tract infection.Upper respiratory tract infection. Caused byCaused by cold virusescold viruses, members of rhinovirus family., members of rhinovirus family. Caused by many types of viruses so development of vaccine is veryCaused by many types of viruses so development of vaccine is very difficult.difficult.
  17. 17. 3.3. EncephalitisEncephalitis It isIt is inflammation of braininflammation of brain caused by virus.caused by virus. Usually caused byUsually caused by arbovirusesarboviruses.. Very serious condition if not treated promptly.Very serious condition if not treated promptly. 4.4. DengueDengue Also known as hemorrhagic fever.Also known as hemorrhagic fever. Characterized by development of high grade fever.Characterized by development of high grade fever. Caused byCaused by arbovirusesarboviruses, transmitted by a mosquito, transmitted by a mosquito called aiedes eygepticus.called aiedes eygepticus. 5.5. Yellow FeverYellow Fever Viral diseases caused byViral diseases caused by arbovirusesarboviruses..
  18. 18. 6.6. RabiesRabies Also known asAlso known as hydrophobiahydrophobia.. Caused byCaused by rhabdovirusrhabdovirus.. These viruses are transmitted by the bite of animalsThese viruses are transmitted by the bite of animals e.g. dog, wolves, bats, etc.e.g. dog, wolves, bats, etc. Prompt treatment by the rabies vaccine is essentialPrompt treatment by the rabies vaccine is essential other wise patient dies.other wise patient dies. 7.7. MeaslesMeasles Caused byCaused by paramyxovirusesparamyxoviruses 8.8. MumpsMumps Caused by paramyxoviruses.Caused by paramyxoviruses. It is inflammation of parotid glands.It is inflammation of parotid glands. A self limiting disease.A self limiting disease.
  19. 19. 9.9. FluFlu Caused by flu viruses.Caused by flu viruses. Spread as a droplet infection.Spread as a droplet infection. Occur in world in epidemic formsOccur in world in epidemic forms
  20. 20. Viral Diseases In PlantsViral Diseases In Plants In plants viral diseases are transmitted eitherIn plants viral diseases are transmitted either by vertical or horizontal transmission.by vertical or horizontal transmission. If plant get viral infection from their parentsIf plant get viral infection from their parents then it is known as vertical transmission.then it is known as vertical transmission. If plant aquired viral infection from someIf plant aquired viral infection from some external source then it is known as horizontalexternal source then it is known as horizontal transmission.transmission.
  21. 21. Different Viral Plant DiseasesDifferent Viral Plant Diseases Viral diseases of plants can stunt their growth andViral diseases of plants can stunt their growth and can even get capability to destroy whole crop.can even get capability to destroy whole crop. Tobacco mosaic disease is a well known viralTobacco mosaic disease is a well known viral infection of plants.infection of plants. Agriculturists are unable to find cure of mostAgriculturists are unable to find cure of most plant disease and they are trying to develop cropsplant disease and they are trying to develop crops which are genetically resistant to viral infections.which are genetically resistant to viral infections.
  22. 22. Acquired Immune Deficiency SyndromeAcquired Immune Deficiency Syndrome Commonly known asCommonly known as AIDSAIDS.. Causative agent is a virus known asCausative agent is a virus known as HIVHIV (human immune(human immune deficiency virus), which is a member of retrovirus group.deficiency virus), which is a member of retrovirus group. HIV binds to specific sites onHIV binds to specific sites on T4 lymphocytesT4 lymphocytes and made themand made them unable to help or induce other white blood cells (e.g. killer cells,unable to help or induce other white blood cells (e.g. killer cells, etc) to work against various microorganisms.etc) to work against various microorganisms. Opportunistic infectionsOpportunistic infections are the cause of death in AIDS patients.are the cause of death in AIDS patients. HIV carriers are those who are infected with HIV but do notHIV carriers are those who are infected with HIV but do not develop AIDS.develop AIDS.
  23. 23. How HIV Transmits ?How HIV Transmits ? Virus can be transmitted byVirus can be transmitted by sexual contact.sexual contact. AIDS can be transmitted by theAIDS can be transmitted by the transfusion oftransfusion of infected bloodinfected blood of patients having HIV.of patients having HIV. HIV can be transmitted in intra venous drug abusersHIV can be transmitted in intra venous drug abusers through infected needles.through infected needles. Close association b/w infected and non infectedClose association b/w infected and non infected peoplepeople (by cuts e.g. surgery on AIDS patient).(by cuts e.g. surgery on AIDS patient). InfectedInfected womanwoman can pass disease tocan pass disease to her newbornher newborn babybaby during pregnancy as well as during the period ofduring pregnancy as well as during the period of breast feeding.breast feeding.
  24. 24. Signs And Symptoms Of AIDSSigns And Symptoms Of AIDS Flu like illnessFlu like illness for a short while after infection is thefor a short while after infection is the 11stst manifestation of AIDS.manifestation of AIDS. After flu like illness patient can usually be symptom lessAfter flu like illness patient can usually be symptom less for months and years.for months and years. Due to deficiency of immune system, opportunisticDue to deficiency of immune system, opportunistic infections start to produces their effects and patientinfections start to produces their effects and patient develops pneumonia and other infections.develops pneumonia and other infections. Other features of AIDS are weight loss, dementia (loss ofOther features of AIDS are weight loss, dementia (loss of memory), and diarrhea.memory), and diarrhea.
  25. 25. Treatment Of AIDSTreatment Of AIDS Scientist is working on two fields to treat AIDS i.e.Scientist is working on two fields to treat AIDS i.e. to control disease and to develop a vaccineto control disease and to develop a vaccine against AIDS.against AIDS. The best available drugs against AIDS areThe best available drugs against AIDS are azidothymidineazidothymidine (also known as zidovudine or(also known as zidovudine or AZT).AZT). AZT slow the progression of disease as well asAZT slow the progression of disease as well as attack on virus present in brain (a major reservoirattack on virus present in brain (a major reservoir of viruses.of viruses.
  26. 26. How To Prevent AIDS ?How To Prevent AIDS ? There is no effective treatment againstThere is no effective treatment against AIDS so disease can be prevented byAIDS so disease can be prevented by acquiring safety measures.acquiring safety measures.
  27. 27. HepatitisHepatitis Hepatitis meansHepatitis means inflammation of liver cellsinflammation of liver cells .. Hepatitis can be caused by variety of agents likeHepatitis can be caused by variety of agents like virus,virus, bacteria, drugs, toxinsbacteria, drugs, toxins, etc., etc. Few sign and symptoms of hepatitis are jaundice,Few sign and symptoms of hepatitis are jaundice, abdominal pain, liver enlargement, fatigue and some timeabdominal pain, liver enlargement, fatigue and some time pyrexia.pyrexia.
  28. 28. Various Types Of HepatitisVarious Types Of Hepatitis 1.1. Hepatitis AHepatitis A Virus transmitted byVirus transmitted by contaminated foodcontaminated food containcontain virus.virus. Contaminated waterContaminated water is major source of infection.is major source of infection. Caused by non enveloped RNA virus.Caused by non enveloped RNA virus.
  29. 29. 2.2. Hepatitis BHepatitis B There are estimatedThere are estimated 200 million carriers200 million carriers ofof hepatitis B in world.hepatitis B in world. Transmitted trough sexual contact, by infectedTransmitted trough sexual contact, by infected blood, by intra venous drug abuse, etc and canblood, by intra venous drug abuse, etc and can lead to liver cancer.lead to liver cancer. VaccineVaccine is available which a best source ofis available which a best source of prevention from hepatitis B.prevention from hepatitis B. Caused by DNA virus.Caused by DNA virus.
  30. 30. 3.3. Hepatitis CHepatitis C Caused by RNA virus and can be transmitted throughCaused by RNA virus and can be transmitted through infected blood, sexual contact (rare), from mother to herinfected blood, sexual contact (rare), from mother to her children, etc.children, etc. Can alsoCan also lead to carrier stagelead to carrier stage.. CausedCaused cirrhosis of livercirrhosis of liver andand liver cancer,liver cancer, if notif not treated promptly.treated promptly. No vaccine is available.No vaccine is available. Acute infections can be treated byAcute infections can be treated by interferoninterferon, which, which can prevent development of carrier stage.can prevent development of carrier stage.
  31. 31. ViroidsViroids Tiny naked, circular RNA molecules.Tiny naked, circular RNA molecules. Infect plants only.Infect plants only. RNA of viroids do not encode proteins in hostRNA of viroids do not encode proteins in host cells.cells. Viroids only replicate their RNA in host cells.Viroids only replicate their RNA in host cells. Stunt growth of host plant cells.Stunt growth of host plant cells.
  32. 32. PrionsPrions Self replicating infecting proteins molecules.Self replicating infecting proteins molecules. Considered as mis folded protein molecules.Considered as mis folded protein molecules. Mechanism of replication is not clear yet.Mechanism of replication is not clear yet. Responsible for many degenerating brainResponsible for many degenerating brain diseases.diseases.

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