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Warm Up. Monday, March 18, 2013 Which process copies a strand of DNA (DNA to DNA)?. Virus Notes. Objectives. List the major components of a virus. 2) List the steps involved in virus replication. - PowerPoint PPT PresentationTRANSCRIPT
Warm Up• Monday, March 18, 2013
• Which process copies a strand of DNA (DNA to DNA)?
Virus Notes
Objectives1)List the major components of a
virus. 2) List the steps involved in virus replication. 3) Describe a real world scenario in which viruses have had a negative impact on human lives.
Viruses• NOT living organisms• Infects host cells• Inject their genetic material into host• Needs host in order to replicate
Parasites= depend entirely
upon another living organism to survive, harming organism in process
• Viruses = parasites• Take advantage of
hosts respiration, nutrition, & all other functions
Virus Genetics• Composed of DNA or
RNA core–Surrounded by protein
coat• Simplest: few genes • Most complex: >100
genes
Capsid= Protein coat that surrounds DNA/RNA• Enable virus to enter
host cell–Bind to receptors on
surface of cell–“Trick” cell into letting it
in–Once inside, viral genes
expressed
Cold Viruses
Viruses Specific• Bind to specific proteins on host
cell’s surface• Why does it matter?
– Infect specific cells– Infect specific organisms
• Example:– HIV infects humans– Parvovirus infects dogs, wolves,
& foxes
Bacteriophage= virus that infects a bacterial cell• Structure:
1) Head = contains DNA2) Neck3) Collar4) Sheath5) Tail Fiber6) Base Plate
Lytic Infection
1. Virus enters cell2. Virus copies
itself3. Cell bursts
Lytic Cycle• 5 Stages:
1) Attachment (a) - virus attaches itself to host cell
2) Injection (a & b) - virus inserts its genetic material into host cell
3) Integration (c) - genetic material tells the cell what to do
4) Replication (d) - host cell builds parts of virus
Assembly (d) - cell assembles replicated parts into progeny viruses 5) Lysis (e)- cell breaks open & ea. replicated virus can infect other cells
Lysogenic Cycle
• Latent period extends cycle
• Viral DNA becomes part of host chromosome for a time
Lysogenic Infection1. Virus enters (a-1)2. Integration: Virus integrates viral DNA
w/ host cell DNA (a-2)3. Viral DNA is replicated (when host cell
replicates DNA) (a-3)4. Host cell completes mitosis & makes
other cells infected w/ virus (a-4)***Difference: Host cell does NOT burst!!!
(b)***
Prophage• Viral DNA that’s
embedded in the host’s chromosome (DNA)
Retrovirus= contain RNA as the hereditary material in place of the more common DNA• Genetic information copied backward
– RNA to DNA (usually other way)• May remain dormant & wait for right
conditions to become active– Dormant = not active (like sleeping)
Retrovirus• Example:
– virus that causes AIDS
– (acquired immune deficiency syndrome)
Viral Diseases• CanNOT be treated w/ antibiotices• Must PREVENT infection
– Vaccinations– Stopping spread
Other Viral Diseases• Chicken Pox
– Symptoms: fever and weakness, red, itchy rash
– Spread By: contact w/ rash– Prevention: Vaccine
Other Viral Diseases
• Measles– Symptoms: High fever, sore throat,
cough, rash, sneezing, swollen eyelids, whiter spots on cheek lining
– Spread By: Droplet inhalation– Prevention: Vaccine
Other Viral Diseases
• West Nile– Symptoms: Fever, headache, body ache- – Spread By: Bite from an infected
mosquito– Prevention: Mosquito repellant, avoid
going outside at dawn & dusk, avoid standing water
AVID Thinking Strategies
• WANTED Virus Poster (2 colors)• Include:
– The words “WANTED” at the top – Virus name – Drawing of virus or picture that depicts
aspect of virus life cycle (Ex: mosquito for west nile)
– Symptoms that are seen in infected host– How virus spread– Prevention/Treatment
Warm Up• Tuesday, March 19, 2013
• Which process creates a strand of RNA (DNA to RNA)?
Germ Warfare Reading & Summaries