Viruses and Prions

Chapter 13

T/F: All viruses have DNA genomes

False

T/F: Viruses can have an outer lipid envelope, similar to cell membranes

True

T/F: Prions are prokaryotic organisms

False

What could be an effective treatment against a prion disease?

Cooking food to a minimum of 165 F

Classifications of viral infections

3 classifications: acute, chronic, and latent

Which classifications of viral infections are considered “persistent”?

Chronic and latent

Acute infection

Short duration (ex: flu)

Chronic infection

Long-lasting (ex: hepatitis)

Latent infection

Recurrent/lifelong (ex: herpes)

Viral structures

Very small, a range of sizes/shapes

Virus

A nucleic acid surrounded by a protein coat

2 main viral structures

Enveloped and non-enveloped

Nucleic acids and viruses

Contain DNA or RNA

Can a virus contain both DNA and RNA?

No - viruses are classified by their nucleic acid content, but they cannot have both DNA and RNA

Shape of viral genomes

Can be circular or linear

Prion

An infectious protein that causes brain lesions

Do prions have DNA or RNA?

No - they lack nucleic acids and are purely protein-based

What types of diseases are spread by prions?

Neurodegenerative diseases

What are 2 modes of transmission for prions?

Contaminated food and medical instruments

How do prions spread?

The prion (PrPsc) causes a healthy protein (PrPc) to misfold, and the misfolded proteins form clumps and cause cell death

What are 2 diseases caused by prions?

Bovine spongiform encephalopathy (mad cow disease), Creudtzfeldt-Jakob disease

What is an example of a viral cancer?

Ovarian cancer can stem from HPV

How are viral cancers spread?

Viral DNA integrates into or replicates within normal cellular DNA

How do viruses invade human cells?

Membrane attachment or endocytosis

T/F: A drug that inhibits cell wall synthesis will be effective in treating a viral infection

False - this works against bacteria, not viruses

Bacteriophage

A virus that only infects bacteria

How do bacteriophages reproduce?

Lytic or lysogenic life cycles

Steps of lytic replication in bacteriophages

1. Phage attachment

2. Genome entry

3. Replication

4. Assembly

5. Lysis

Steps of lysogenic replication in bacteriophages

1. Phage attachment

2. Genome entry

3. Genome integration

4. Signal to lytic life cycle

T/F: Not all bacteriophages are helpful

True - some integrated phage DNA encodes toxins (ex: botulinum toxin)