Virus Drill 1 1. What are the two essential components of a virus? 2. How do viroids & prions compare to viruses? 3. Name three differences between viruses.

Virus Drill 1Virus Drill 11.1. What are the two essential What are the two essential

components of a virus?components of a virus?

2.2. How do viroids & prions compare to How do viroids & prions compare to viruses?viruses?

3.3. Name three differences between Name three differences between viruses & cells.viruses & cells.

Virus Drill 2Virus Drill 2

1. List the stages of the lytic cycle.1. List the stages of the lytic cycle.

2. Describe the structure of the 2. Describe the structure of the bacteriophage.bacteriophage.

3. Define a prophage.3. Define a prophage.

4. How do scientist’s believe the first 4. How do scientist’s believe the first viruses evolved?viruses evolved?

Virus Drill 3Virus Drill 3

1. Explain why viruses are non living.1. Explain why viruses are non living.

2. Define the following…2. Define the following…– CapsidCapsid– SpikesSpikes– EnvelopedEnveloped– Naked Naked

3. What are the 3 common shapes of 3. What are the 3 common shapes of viruses?viruses?

Virus Drill 4Virus Drill 4

1.1. What are the three ways a virus can What are the three ways a virus can interact with the host cell?interact with the host cell?

2. What does lytic mean?2. What does lytic mean?

3. What are the stages of the lytic life 3. What are the stages of the lytic life cycle? Name a virus that uses the cycle? Name a virus that uses the lytic cycle?lytic cycle?

Drill 5Drill 5

Define a virus.Define a virus.

What are the outer of virus called?What are the outer of virus called?

Explain why viruses are non living.Explain why viruses are non living.

Drill 6Drill 6 Define and give an example of a zoonotic Define and give an example of a zoonotic

disease.disease.

How is a persistent disease different from an How is a persistent disease different from an acute disease? Give examples of each.acute disease? Give examples of each.

What is meant by a latent virus? Give an What is meant by a latent virus? Give an example of it.example of it.

How are chronic viruses different from slow How are chronic viruses different from slow infections? Give an example of each.infections? Give an example of each.

Virus 7Virus 7

1.1. Describe the lytic life Describe the lytic life cycle.cycle.

2.2. Describe the lysogenic Describe the lysogenic life cycle.life cycle.

Virus 8Virus 8

1. What is the difference between 1. What is the difference between active & passive immunity?active & passive immunity?

2. Why are antibiotics not effective 2. Why are antibiotics not effective against viruses?against viruses?

3. What is a vaccine & how is it useful?3. What is a vaccine & how is it useful?

VirusVirus

VirusesVirusesI. General CharacteristicsI. General Characteristics

A. Non- living agentsA. Non- living agents

Lacking energy - ATPLacking energy - ATPLacking organelles (Ribosomes)Lacking organelles (Ribosomes)Has DNA or RNA, but not bothHas DNA or RNA, but not bothCan only grow within living cellsCan only grow within living cellsHas 2 phases in their life cycleHas 2 phases in their life cycle

Outside - dead - metabolically inert - only considered a Outside - dead - metabolically inert - only considered a macromolecule.macromolecule.

Inside - living- uses host machinery to produce virons Inside - living- uses host machinery to produce virons (Viruses).(Viruses).

II. SizeII. Size

Variety of shapes but size is well below the limit of Variety of shapes but size is well below the limit of visibility in a light microscope.visibility in a light microscope.

100 - 1,000 X’s smaller than the cells they infect (20 100 - 1,000 X’s smaller than the cells they infect (20 - 250 nm).- 250 nm).

III Shapes & DesignIII Shapes & Design

A. PolyhedralA. PolyhedralB. HelicalB. HelicalC. CombinationC. CombinationD. Enveloped -lipid layer acquired from the infected D. Enveloped -lipid layer acquired from the infected

cell’s membrane during the release of the virus cell’s membrane during the release of the virus or Naked.or Naked.

E. Capsid - protein coat for protectionE. Capsid - protein coat for protectionF. Nucleic AcidsF. Nucleic Acids

1. DNA - double (rare) or single stranded - 1. DNA - double (rare) or single stranded - contains all the genetic information in a contains all the genetic information in a singular linear molecule.singular linear molecule.

2. RNA - double (rare) or single.2. RNA - double (rare) or single.G. Capsomere - Identical protein sub-units.G. Capsomere - Identical protein sub-units.H. Nucleocapsid - viral capsid with it’s nucleic acid.H. Nucleocapsid - viral capsid with it’s nucleic acid.I. Spikes - Attachment proteins.I. Spikes - Attachment proteins.

IV. Viral & Host’s InteractionsIV. Viral & Host’s Interactions

A. Little is understood between viruses & animal A. Little is understood between viruses & animal cell’s because of the complexity of the animal cell.cell’s because of the complexity of the animal cell.

10,000 X Bigger DNA10,000 X Bigger DNA1,000 X bigger1,000 X bigger100 X longer to divide100 X longer to divide

B. Viruses can have different relationships to their B. Viruses can have different relationships to their host cell.host cell.

May kill it.May kill it.May become apart of the hosts genomeMay become apart of the hosts genomeModify properties of the cell.Modify properties of the cell.

V. Life CyclesV. Life CyclesA. Virulent or Lytic Life cycle - Host cell always dies.A. Virulent or Lytic Life cycle - Host cell always dies.DNA VirusDNA Virus

1. Attachment - Virus attaches to host cell at 1. Attachment - Virus attaches to host cell at receptors.receptors.

2. Entry - Viral N.A. enters the cell. 2. Entry - Viral N.A. enters the cell. (Lysozymes enzymes degrade the bacterial cell (Lysozymes enzymes degrade the bacterial cell

wall & DNA is injected into the cell.wall & DNA is injected into the cell.3. Replication 3. Replication

a. Phage -induced proteins - First enzymes to a. Phage -induced proteins - First enzymes to be produced by the viral DNA.be produced by the viral DNA.

Nuclease - degrades the host’s cell’s Nuclease - degrades the host’s cell’s DNA DNA (early).(early).

Enzymes that lyses the bacteria’s cell Enzymes that lyses the bacteria’s cell wall wall (late).(late).

b. Vegetative Replication - New viral b. Vegetative Replication - New viral components are components are produced.produced.

4. Assembly (maturation) - Viral components self 4. Assembly (maturation) - Viral components self asemby asemby (no enzymes are needed).(no enzymes are needed).

5. Release5. Releasea. Enzymes degrade the bacteria’s cell wall a. Enzymes degrade the bacteria’s cell wall

(weak).(weak).b. Viruses burst out of the cell which kills it.b. Viruses burst out of the cell which kills it.c. Releases up to 200 new viruses.c. Releases up to 200 new viruses.

ReviewReview

What are the stages of the lytic What are the stages of the lytic cycle?cycle?

What are the three basic shapes of a What are the three basic shapes of a virus?virus?

B. Temperate or Lysogenic - DNA becomes integrated into the host’s B. Temperate or Lysogenic - DNA becomes integrated into the host’s genetic material genetic material

Prophage or Provirus - Viral DNA that has been incorporated into Prophage or Provirus - Viral DNA that has been incorporated into the host cell.the host cell.Lysogenic or lysogen - Bacterial cell carrying the prophage.Lysogenic or lysogen - Bacterial cell carrying the prophage.

1. Attachment - Virus attaches to host cell at receptors.1. Attachment - Virus attaches to host cell at receptors.2. Entry - Viral N.A. enters the cell 2. Entry - Viral N.A. enters the cell & is integrated into the & is integrated into the

host cells host cells DNA. DNA. (Lysozymes enzymes degrade the bacterial cell wall (Lysozymes enzymes degrade the bacterial cell wall

& DNA & DNA is injected into the cell.is injected into the cell.3. Repressed or Dormant.3. Repressed or Dormant.

Repressor must function continuously.Repressor must function continuously.Could last indefinitely.Could last indefinitely.

Lysogenic cell is immune to further Lysogenic cell is immune to further infections from infections from the same virus but not different the same virus but not different ones.ones.

Lysogenic conversion - Prophage gives the Lysogenic conversion - Prophage gives the cell new cell new properities.properities.

Corynebacterium diphtheriaeCorynebacterium diphtheriae - - diptheriadiptheria

Streptoccus pyogenesStreptoccus pyogenes - scarlet fever - scarlet feverClostridium botulinumClostridium botulinum - botulism - botulism

4. Induction to lytic cycle.4. Induction to lytic cycle.Propahge becomes active for any reason.Propahge becomes active for any reason.Activation of the SOS repair which destroys the Activation of the SOS repair which destroys the

repressor.repressor.

ReviewReview

What are the stages of the lysogenic What are the stages of the lysogenic cycle?cycle?

Can the lysogenic cycle stay dormant Can the lysogenic cycle stay dormant forever? What can trigger the forever? What can trigger the lysogenic cycle to go lytic?lysogenic cycle to go lytic?

C. Filamentous PhagesC. Filamentous Phages

Extrusion - Constantly releases new viruses Extrusion - Constantly releases new viruses without being destroyed.without being destroyed.

Carrier cells - infected cells.Carrier cells - infected cells.1. Long & thin1. Long & thin2. Infect only 2. Infect only E. coliE. coli (F+). (F+).3. Do not completely take over the host 3. Do not completely take over the host

cells cells metabolism.metabolism.4. Can not be detected in the cytoplasm of 4. Can not be detected in the cytoplasm of

the host the host cell, maybe stored in the cell’s cell, maybe stored in the cell’s membrane.membrane.

D. TransductionD. Transduction

Bacterial DNA is transferred from one bacteria to another Bacterial DNA is transferred from one bacteria to another by either replacing or tagging along with viral DNA.by either replacing or tagging along with viral DNA.

1. Generalized Transduction - replaces viral DNA1. Generalized Transduction - replaces viral DNA

Both Virulent & Temperate life cycles.Both Virulent & Temperate life cycles.

Pieces of bacterial DNA fragments are placed into Pieces of bacterial DNA fragments are placed into the capsid the capsid instead of viral.instead of viral.

Transferred to another bacteria & integrated In the Transferred to another bacteria & integrated In the new new bacteria’s DNA.bacteria’s DNA.

Does not kill the bacteria because the viral genetic Does not kill the bacteria because the viral genetic information information to do that is missing or replaced by bacterial to do that is missing or replaced by bacterial DNA - known as a DNA - known as a defective phage.defective phage.

2. Specialized Transduction - tags along with viral DNA2. Specialized Transduction - tags along with viral DNA

Only temperate viruses can carry them.Only temperate viruses can carry them.

ReviewReview

How is a filamentous virus different How is a filamentous virus different from lytic and lysogenic?from lytic and lysogenic?

Define transduction.Define transduction.

How is generalized different from How is generalized different from specialized?specialized?

VI. Host Range of VirusesVI. Host Range of Viruses

Viruses can only infect a certain range of cells - Host Viruses can only infect a certain range of cells - Host range.range.

ex. Bacteria, fungi, algae, pants, & animalsex. Bacteria, fungi, algae, pants, & animals

Some are specific T4 - only with bacteria, Polio - only Some are specific T4 - only with bacteria, Polio - only with humanswith humans

Some may be wider – rabiesSome may be wider – rabies

Determine by the presence of absence of receptors Determine by the presence of absence of receptors on the host cell needed by the virus to attach.on the host cell needed by the virus to attach.

VII Animal VirusesVII Animal VirusesA. ClassificationA. Classification

1. Nucleic Acids - single of double stranded DNA or 1. Nucleic Acids - single of double stranded DNA or RNA.RNA.

2. Capsid shape.2. Capsid shape. 3. Presence or absence of an envelope.3. Presence or absence of an envelope. 4. Size.4. Size. 5. Route of transmission.5. Route of transmission.

a. Enteric viruses - ingested on material a. Enteric viruses - ingested on material contaminated by feces.contaminated by feces.

b. Respiratory viruses.b. Respiratory viruses. c. Zoonosis - animal to human.c. Zoonosis - animal to human. d. Sexually transmitted viruses. d. Sexually transmitted viruses.

6. Strategy of viral replication.6. Strategy of viral replication.

B. Interaction of Animal Viruses with their Hosts.B. Interaction of Animal Viruses with their Hosts. 1. Acute1. Acute

.Fast acting.Fast acting

.Remains localized.Remains localized

.Mumps, measles, flu.Mumps, measles, flu

2. Persistent Infections - always present in the body. 2. Persistent Infections - always present in the body. Late Complications - Subacute sclerosing Late Complications - Subacute sclerosing panencephalitis (SSPE)panencephalitis (SSPE)

.Follows measles.Follows measles

.10 years after infection.10 years after infection

.1 in 300,000.1 in 300,000

.Onset, few viruses in brain..Onset, few viruses in brain.

.Nerve cells prevent viral replication..Nerve cells prevent viral replication.

b. Latent Infections - Infectious particles cannot be b. Latent Infections - Infectious particles cannot be detected until reactivation of the disease.detected until reactivation of the disease.

1. Herpes (HSV-1, HSV-2)1. Herpes (HSV-1, HSV-2)

Initial infection is acute, may not lead to ay Initial infection is acute, may not lead to ay symptoms.symptoms.

Infects sensory nerve cells where it Infects sensory nerve cells where it remains remains non-infectious.non-infectious.

Replication of viruses remains suppressed.Replication of viruses remains suppressed.

Activated by stress - fever, sunburn.Activated by stress - fever, sunburn.

Infectious viruses are produced & carried Infectious viruses are produced & carried to the to the skin = cold sore.skin = cold sore.

Cold sores heal, virus is dormant again.Cold sores heal, virus is dormant again.

2. Chicken Pox (varicella- another member of the 2. Chicken Pox (varicella- another member of the herpes family).herpes family).

Initial infection - rashInitial infection - rash

Remains latent for yearsRemains latent for years

Reactivated - shingles (herpes zoster).Reactivated - shingles (herpes zoster).

c. Chronic Infections - demonstrated all the time.c. Chronic Infections - demonstrated all the time.

Hepatis B (serum hepatitis)Hepatis B (serum hepatitis)Carrier state - can be detected in body fluids.Carrier state - can be detected in body fluids.Plasmid state - integrated into the liver cellsPlasmid state - integrated into the liver cells

d. Slow Infections - Infection gradually increases d. Slow Infections - Infection gradually increases over over time.time.

1. AIDS1. AIDS

e. Prions - Self replicating protein the causes e. Prions - Self replicating protein the causes neurological neurological diseases in humans.diseases in humans.

C. Oncogenic Viruses - RNA - causes cancerC. Oncogenic Viruses - RNA - causes cancer1. Retro viruses - group of RNA viruses that produces 1. Retro viruses - group of RNA viruses that produces

cancercancer

Nondefective - replicates independently within the Nondefective - replicates independently within the host cell.host cell.

Rapid transformationRapid transformationDefective - requires a helper virus - malignanciesDefective - requires a helper virus - malignancies

VIII. Plant Viruses - Majority are ssRNA (+) or (-)VIII. Plant Viruses - Majority are ssRNA (+) or (-)A. Economic importance, a serious infection may reduce A. Economic importance, a serious infection may reduce

crop yield by 50%.crop yield by 50%.B. Localized abnormalities.B. Localized abnormalities.

Discoloration due to the destruction of chlorophyllDiscoloration due to the destruction of chlorophyllTumorsTumorsDeformed structuresDeformed structuresSometime it’s desired - colors in tulipsSometime it’s desired - colors in tulips

C. Transmission C. Transmission 1. Infection due to injury to part of the plant which 1. Infection due to injury to part of the plant which permits the virus permits the virus to enter.to enter.2. Contaminated soil from other infected plants.2. Contaminated soil from other infected plants.3. Insect, worms, fungi, human handling.3. Insect, worms, fungi, human handling.a. Temporary transmission - virus is associated a. Temporary transmission - virus is associated around the mouth parts of the vector.around the mouth parts of the vector.b. Circulative transmission - virus circulates but b. Circulative transmission - virus circulates but does not replicate in the insects body.does not replicate in the insects body.c. Replication of virus in the insect, infects both c. Replication of virus in the insect, infects both insect & plant.insect & plant.Aphid & Leaf hoppersAphid & Leaf hoppers

D. ViroidD. Viroid

1. Unprotected ssRNA found ONLY in plants.1. Unprotected ssRNA found ONLY in plants.

2. 1/10 the size of the smallest known RNA virus.2. 1/10 the size of the smallest known RNA virus.

E. Satellite VirusesE. Satellite Viruses

1. Can only replicate if a HELPER Virus is present 1. Can only replicate if a HELPER Virus is present with in the same infect cell.with in the same infect cell.

ReviewReview How many crops are affected by viruses each How many crops are affected by viruses each

year?year?

How can viruses that infect plants be spread?How can viruses that infect plants be spread?

What is a viroid? How is it different from What is a viroid? How is it different from prions?prions?

How is a satellite virus different from a regular How is a satellite virus different from a regular virus?virus?