HAPPY THURSDAY

Bellwork: What is a virus? How do viruses make

us sick? How are viral infections treated? Can viral infections be

prevented? Write 37 words on the topic.

Essential Question:

How do viruses spread and cause disease?

Standard: describe the role of viruses in causing diseases such as human immunodeficiency virus (HIV)

(B4C)

Our new unit:Viruses

Virus and Microorganisms NotecardsPre-AP Biology

Due Thursday (2/12/15)

I. VirusesA. All viruses have one thing in common:

1. They enter living cells and use the cell to produce more viruses.

B. Virus Structure-A virus is made of:

a) a core of DNA or RNAb) A virus has either a capsid or an envelope surrounding its genetic information.

-The capsid allows viral DNA or RNA to enter a host cell.Envelope

Capsid

Viral components

– Nucleic acids• DNA or RNA

– Capsid• Protein

– Envelope• Lipid

– Spikes• Used to attach to cell• ONLY SOME VIRUSES 7

Generalized Structure of Viruses

virions having envelopes = enveloped viruses

virions lacking envelopes = naked viruses

Generalized Structure of Viruses

9

10

Cellular Organisms vs Acellular Particles

Eukaryotic Nucleus

Prokaryotic Cell

Virus

Eukaryotic Cell

1 ųm (1000 nm)

C. Virus Specificity -Viruses are highly specific to the cells they infect

Examples: 1) plant viruses infect plant cells2) animal viruses infect only certain related species of animals3) bacterial viruses infect only certain types of bacteria.

So, what about zombies?

E. Retroviruses1. Retroviruses are viruses that contain RNA as their genetic information.-Retroviruses get their name from the fact that their genetic information is copied backward, from RNA to DNA.2. HIV is the most infamous retrovirus.

AZT is a medication used to treat HIV by stopping an enzyme

called reverse transcriptase

Write this on your notes!

F. Viruses are parasites (use other organisms to grow and reproduce)

1. Viruses are NOT alive because they do not:

a) grow and developb) obtain and use

energyc) respond to the environment

G. Vaccines1. Viral diseases cannot be treated with antibiotics.2. Vaccines are the best way to protect against viruses

a) A vaccine is a dead or weakened version of a virus that is injected into a person to stimulate the immune system.b) Vaccines provide protection only if they are used before an infection begins.

When a virus invades…

D. Most viruses are not harmful to humans.1. A pathogen is a disease-causing agent.2. Viruses cause disease by disrupting the body’s normal equilibrium.3. Viruses attack and destroy certain cells in the body, causing the symptoms of the disease.

H. Viral Reproduction1. Once viral genes are inside the host cell, two processes

may occur: the lytic cycle or the lysogenic cycle.

Lytic Cyle

a) Lytic Cycle1. Viral genes are inserted into a host cell and take control of the cell2. After more viruses are made, the host cell bursts and is destroyed3. New viruses infect new host cells

b) Lysogenic Cycle 1. Virus makes its DNA a part of the host cell’s DNA

(integrates) 2. Virus’s genetic information (DNA or RNA) replicates with the host cell’s DNA.

3. The DNA remains dormant in the host cell. 4. Virus’s DNA activates and switches back to the

lytic cycle.

DRAW THIS!!!

- Since viruses can transport DNA and RNA into cells, scientists are exploring Gene Therapy

- In Gene Therapy, viral genetic material is replaced with new DNA

- In time, this could be used to cure genetic diseases. Currently we have no cure for these types of illnesses

c) Viral diseases result in cell death

Sage and Scribe: Cycle Steps

• Get into partners—decide who is partner A and who is partner B.–Partner A: Describe the steps for the Lytic

cycle.–Partner B: Draw each step.

• After a few minutes, we will switch to the Lysogenic Cycle and you will switch roles.