Viruses & PrionsViruses & Prions

What is a virus???What is a virus???

A virus is neither dead nor alive!A virus is neither dead nor alive!

What is to be alive?What is to be alive?

Characteristics for life...Characteristics for life...

1. Metabolism1. Metabolism 2. Reproduction2. Reproduction 3. DNA3. DNA 4. Growth & Development4. Growth & Development 5. Response to environment5. Response to environment 6. Maintain internal environment6. Maintain internal environment 7. Evolves 7. Evolves

Living organisms do not crystallize - Living organisms do not crystallize - viruses do.  viruses do.  

Viruses are made-up of either DNA Viruses are made-up of either DNA (like smallpox) or RNA (flu, HIV) and (like smallpox) or RNA (flu, HIV) and protein.  Some viruses also have protein.  Some viruses also have lipids.lipids.

A virus is basically a protein container A virus is basically a protein container (capsid) with nucleic acid inside.  The (capsid) with nucleic acid inside.  The only purpose of viruses is to only purpose of viruses is to reproduce. reproduce.

A virus is not considered alive since it must A virus is not considered alive since it must hijack the machinery of cells to copy itself.hijack the machinery of cells to copy itself.

Viruses are generally specific as to what Viruses are generally specific as to what they infect.  they infect.  

Plant viruses like the Tobacco Mosaic Virus, Plant viruses like the Tobacco Mosaic Virus, infect tobacco plantsinfect tobacco plants

Animal viruses like influenza, infect certain Animal viruses like influenza, infect certain animals (humans, pigs, ducks)animals (humans, pigs, ducks)

Viruses that infect bacteria are called a Viruses that infect bacteria are called a bacteriophage. bacteriophage.

Influenza VirusInfluenza Virus

Tobacco Mosaic VirusTobacco Mosaic Virus

Potato VirusPotato Virus

T4 BacteriophageT4 Bacteriophage

Viral infectionViral infection

When a virus has infected an organisms, When a virus has infected an organisms, there are two processes that can occur:there are two processes that can occur:

LyticLytic infection or infection or LysogenicLysogenic infection infection

In In lytic infectionlytic infection - as is the case with - as is the case with bacteriophage T4 - a virus enters a cell, bacteriophage T4 - a virus enters a cell, makes copies, and causes the makes copies, and causes the cell to burst (Lyses).cell to burst (Lyses).

In lysogenic infection the virus integrates its In lysogenic infection the virus integrates its genetic material into the DNA of its host. genetic material into the DNA of its host.  Then the host cell  Then the host cell replicates its DNA along with the viral DNA - replicates its DNA along with the viral DNA - thus producing viruses indefinitely. thus producing viruses indefinitely.

RetrovirusRetrovirus

These viruses contain RNA instead of DNA as These viruses contain RNA instead of DNA as their genetic material.  A retrovirus gets its their genetic material.  A retrovirus gets its name "retro - name "retro - meaning backwards" because it copies RNA to meaning backwards" because it copies RNA to DNA.DNA.

Retroviruses can cause cancer in animals and Retroviruses can cause cancer in animals and some are well known such as HIV and some are well known such as HIV and Influenza.Influenza.

Reverse Transcriptase??? Reverse Transcriptase??? ViroidsViroids

Single-stranded RNA particle without capsid ~ Single-stranded RNA particle without capsid ~ usually a plant affecting disease. usually a plant affecting disease.

RetrovirusRetrovirus

Chicken Pox (Varicella)Chicken Pox (Varicella)

Measles (MMR)Measles (MMR)

Smallpox (Variola)Smallpox (Variola)

Eradicated, but what about Eradicated, but what about terrorism?terrorism?

SmallpoxSmallpox

PRIONS???PRIONS???

Mad Cow Disease or BSE (Bovine Spongiform Encephalopathy) and varient Creutzfeld-Jacob disease - the human form - Mad Cow Disease or BSE (Bovine Spongiform Encephalopathy) and varient Creutzfeld-Jacob disease - the human form - are thought to be caused by pathogenic proteins called prions.are thought to be caused by pathogenic proteins called prions.

MAD COW DISEASEMAD COW DISEASE Mad cow disease is caused by Mad cow disease is caused by

something called a "PRION". A something called a "PRION". A prion is a protein that is mutant prion is a protein that is mutant (different than the normal kind) and (different than the normal kind) and causes normal proteins to change causes normal proteins to change into mutant proteins when they into mutant proteins when they come into contact with them. come into contact with them.

These pathogenic (disease causing) These pathogenic (disease causing) proteins can be obtained by eating proteins can be obtained by eating tissue that contains it (like cow tissue that contains it (like cow brains from an infected cow). brains from an infected cow).

It can also be passed down from It can also be passed down from mother to offspring animal ~ cow mother to offspring animal ~ cow (inherited). This is possible because (inherited). This is possible because proteins are built from the proteins are built from the instructions found in the organism's instructions found in the organism's genes (DNA). If the organism has a genes (DNA). If the organism has a bad gene for this disease, it will be bad gene for this disease, it will be passed to the offspring.passed to the offspring.

The EndThe End