VirusesViruses

Bacteriophage: Virus that infect a bacteria

Protein coat that surrounds the RNA or DNA

Contains DNA or RNA

Viruses - particles of Viruses - particles of nucleic acid , proteinnucleic acid , protein and sometimes and sometimes lipidslipids that can reproduce that can reproduce only by entering a cell (host). They are only by entering a cell (host). They are considered non-living.considered non-living.

Viruses are Viruses are parasitesparasites responsible for responsible for causing many diseases in living things causing many diseases in living things (herpes and HIV in humans, for example).(herpes and HIV in humans, for example).

Viruses are found everywhere.Viruses are found everywhere.

Viruses consist of aViruses consist of a core of nucleic acid, core of nucleic acid, either DNA or RNA, and a protective either DNA or RNA, and a protective coat of protein molecules and coat of protein molecules and sometimes lipids. sometimes lipids.

Viruses -

In isolation, viruses and bacteriophages In isolation, viruses and bacteriophages show none of the expected signs of life. show none of the expected signs of life. They do not respond to stimuli, they do not They do not respond to stimuli, they do not grow, they do not do any of the things we grow, they do not do any of the things we normally associate with life. normally associate with life.

Strictly speaking, they should not be Strictly speaking, they should not be considered "living" organisms at all. considered "living" organisms at all. However, they are more complex than a However, they are more complex than a lifeless collection of macromolecules and lifeless collection of macromolecules and they do show one of the most important they do show one of the most important signs of life: the ability to signs of life: the ability to reproduce at reproduce at a fantastic rate but only in a host a fantastic rate but only in a host cellcell..

Bacteriophages attack Bacteriophages attack bacteria (prokaryotes)bacteria (prokaryotes)

viruses attack eukaryotic viruses attack eukaryotic cells.cells.

Viruses and bacteriophages invade cells and Viruses and bacteriophages invade cells and use the host cell's machinery to synthesize use the host cell's machinery to synthesize more of their own macromoleculesmore of their own macromolecules..

Lytic CycleLytic Cycle - - the virus enters the cell makes copies the virus enters the cell makes copies

of itself and causes the cell to burst.of itself and causes the cell to burst. oror

Lysogenic CycleLysogenic Cycle – – The virus intergrates its DNA into The virus intergrates its DNA into

the DNA of the host cell, then the the DNA of the host cell, then the viral genetic information viral genetic information replicates along with the host replicates along with the host cell’s DNA.cell’s DNA.The cell does not burst.The cell does not burst.

The Lytic CycleThe Lytic Cycle

The Lysogenic CycleThe Lysogenic Cycle

A A retrovirusretrovirus injects the enzyme, injects the enzyme, reverse transcriptase into the cell to reverse transcriptase into the cell to copy viral RNA into DNAcopy viral RNA into DNA..

A A provirusprovirus is a DNA virus that is a DNA virus that has been inserted into a host has been inserted into a host cell chromosomecell chromosome

RETROVIRUSESRETROVIRUSES

BACK

What does bacteria have to do with DNA What does bacteria have to do with DNA technology?technology?

Bacteria are simpleBacteria are simple Bacteria have DNA that is made of nucleotides Bacteria have DNA that is made of nucleotides

(A,T,G,C)(A,T,G,C) Bacteria can be grown quickly and easilyBacteria can be grown quickly and easily

Give them food, warmth and dark (like inside you shoe) Give them food, warmth and dark (like inside you shoe) and they will multiply like mad (binary fission)and they will multiply like mad (binary fission)

PLASMIDSPLASMIDS Plasmids are DNA – made out of A,T,C,G Plasmids are DNA – made out of A,T,C,G

nucleotidesnucleotides

The same nucleotides found in human DNA, The same nucleotides found in human DNA, plant DNA, dog DNA, fish DNA, fungus DNAplant DNA, dog DNA, fish DNA, fungus DNA

Get it – it’s all the same moleculeGet it – it’s all the same molecule

HIV HIV is ais a retrovirus injecting the retrovirus injecting the enzyme, reverse transcriptase into enzyme, reverse transcriptase into the cell to copy viral RNA into DNAthe cell to copy viral RNA into DNA. .

Viruses are host specific – a protein on the surface of the virus has a shape that matches a molecule in the plasma membrane of its host, allowing the virus to lock onto the host cell.

HIVHIV doesn’t target just any cell, it goes right for the cells that want to doesn’t target just any cell, it goes right for the cells that want to kill it. “Helper" T cells are HIV's primary target. These cells help kill it. “Helper" T cells are HIV's primary target. These cells help direct the immune system's response to various pathogens. direct the immune system's response to various pathogens.

HIV undermines the body's ability to protect HIV undermines the body's ability to protect against disease by depleting T cells thus against disease by depleting T cells thus destroying the immune systemdestroying the immune system..

The virus can infect 10 billion cells a day, yet The virus can infect 10 billion cells a day, yet only 1.8 billion can be replaced daily.only 1.8 billion can be replaced daily.

After many years of a constant battle, the body has After many years of a constant battle, the body has insufficient numbers of T-Cells to mount an immune insufficient numbers of T-Cells to mount an immune response against infections. At the point when the response against infections. At the point when the body is unable to fight off infections, a person is said body is unable to fight off infections, a person is said to have the disease to have the disease AIDSAIDS..

It is not the virus or the disease that ultimately kills a It is not the virus or the disease that ultimately kills a

person; it is the inability to fight off something as person; it is the inability to fight off something as minor as the common cold. minor as the common cold.

The four main fluids that The four main fluids that HIV is transmitted by areHIV is transmitted by are::

BloodBlood Breast milkBreast milk SemenSemen Vaginal dischargeVaginal discharge

What are vaccines?What are vaccines? A vaccine is a substance that A vaccine is a substance that

stimulates the body’s immune stimulates the body’s immune responseresponse..

The goal of vaccination is to The goal of vaccination is to prevent or control an infection. prevent or control an infection.