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

Flu Virus

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