Viruses and HIV

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In the lysogenic cycle, the virus reproduces by first injecting its genetic material, indicated by the red line, into the host cell's genetic instructions.

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Viruses Enter Living Cells

Viruses enter bacterial cells by punching a hole in the cells wall and injecting its DNA

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Viruses Enter Living Cells

Viruses enter plant cells through tiny rips in the cell wall.

Viruses enter animal cells by endocytosis.

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Mutating viruses

Viruses can mutate when they copy the genetic material

Copy something wrong

Mistake proves useful

More powerful virus (more infectious)

Viruses don’t mutate often, except…

Influenza

HIV

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Viruses are host cell specific.

Most viruses are restricted to certain kinds of cells (those that infect plants cannot infect animal cells).

Why?

Scientists think that viruses originated from escaped genetic material from host cells.

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Viruses can be beneficial…

Bacteriophages – attack & destroy bacteria

Baculovirus – ebola-like virus that attacks insects

Could use for pest control in crops

Cabbage loopers eat

cabbage crops

Virus can kill pests in days

(it’s really gross)

… and then there are those that are not so good….

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The spread of West Nile virus (1999 – 2002) – bird, horse, mosquito or human

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Also important…

Any agent (not just viruses) that causes disease is a pathogen.

When a virus inserts its genetic material into a host’s DNA, it is called a provirus.

Some viruses replicate very slowly and only cause damage when the conditions are “right”. (cold sores)

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Human Immunodeficiency Virus (HIV) Acquired Immuno Deficiency Syndrome (AIDS)

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Basic Structure

Viral envelope – lipid bilayer; glycoproteins protrude from surface

Glycoproteins enable virus to recognize surface proteins of special immune cells and to enter the cell (like a key to the cell’s door)

2 strands RNA – only 9 genes; 3 are found in many viruses (structural proteins)