VIRUS Notes

Definition Viruses are tiny particles unlike any other organism. A virus consists of genetic material such as RNA or DNA wrapped in a protein coat. Viruses are tiny particles unlike any other organism. A virus consists of genetic material such as RNA or DNA wrapped in a protein coat.

Characteristics of Life Homeostasis Homeostasis Nutrition Nutrition Transport Transport Respiration Respiration Synthesis Synthesis Growth Growth Excretion Excretion Regulation Regulation Reproduction Reproduction Is a virus living? Is a virus living?

Is it living? No, because a virus can not reproduce on its own. It needs a host cells. No, because a virus can not reproduce on its own. It needs a host cells.

How does a virus’ size relate to the size of the cell? Viruses are much smaller than a cell and that is why they can easily get into a cell Viruses are much smaller than a cell and that is why they can easily get into a cell

How are viruses characterized? Characterized as: Characterized as: Plant virus Plant virus Animal virus Animal virus Bacterial virus (bacteriophage) Bacterial virus (bacteriophage)

What are the two parts that comprise a virus? Nucleic Acid Core (either RNA or DNA) Nucleic Acid Core (either RNA or DNA) Protein Coat called a capsid Protein Coat called a capsid

Shapes of Viruses 1. Rod shaped (tobacco mosaic virus) 1. Rod shaped (tobacco mosaic virus)

Shapes of Virus 2. Polyhedral (Mumps) 2. Polyhedral (Mumps)

Shapes of Virus 3. Helical (Herpes) 3. Helical (Herpes)

How does a DNA virus replicate? DNA virus produces RNA (transciption) DNA virus produces RNA (transciption) RNA directs production of viral proteins RNA directs production of viral proteins OR OR Viral DNA combines with host cell’s DNA (either plant or animal) Viral DNA combines with host cell’s DNA (either plant or animal)

How does RNA virus replicate or reproduce itself? Once inside the host, an RNA virus directs the host cell to produce proteins Once inside the host, an RNA virus directs the host cell to produce proteinsOR Viral RNA may make DNA Viral RNA may make DNA

Retrovirus Virus that has RNA as its genetic material Virus that has RNA as its genetic material Example is HIV Example is HIV

Bacteriophage Virus that attacks a bacterial cell Virus that attacks a bacterial cell Two types of infection: A. Lytic Cycle B. Lysogenic Cycle

Lytic Cycle Bacteriophage attaches to host cell and injects its DNA Bacteriophage attaches to host cell and injects its DNA Foreign DNA produces more proteins in the host cell Foreign DNA produces more proteins in the host cell Causes cell to lyse (or break open) and the virus/phage is released into the host’s body Causes cell to lyse (or break open) and the virus/phage is released into the host’s body

Lytic Cycle

Lysogenic Cycle Phage injects DNA into the host cell Phage injects DNA into the host cell Foreign/phage DNA integrates itself into a chromosome Foreign/phage DNA integrates itself into a chromosome Bacteria reproduces Bacteria reproduces

Lysogenic Cycle

Lytic vs.Lysogenic Cycle