VIRUS NotesVIRUS Notes

DefinitionDefinition

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

Characteristics of LifeCharacteristics of Life HomeostasisHomeostasis NutritionNutrition TransportTransport RespirationRespiration SynthesisSynthesis GrowthGrowth ExcretionExcretion RegulationRegulation ReproductionReproduction

Is a virus living?Is a virus living?

Is it living?Is it living?

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

How does a virus’ size relate to the How does a virus’ size relate to the size of the cell?size of the cell?

Viruses are much smaller than a cell and Viruses are much smaller than a cell and that is why they can easily get into a cellthat is why they can easily get into a cell

How are viruses characterized?How are viruses characterized?

Characterized as:Characterized as:Plant virusPlant virusAnimal virusAnimal virusBacterial virus (bacteriophage)Bacterial virus (bacteriophage)

What are the two parts that What are the two parts that comprise a virus?comprise a virus?

Nucleic Acid Core Nucleic Acid Core (either RNA or DNA)(either RNA or DNA)

Protein Coat called a Protein Coat called a capsidcapsid

Shapes of VirusesShapes of Viruses

1. Rod shaped 1. Rod shaped (tobacco mosaic (tobacco mosaic virus)virus)

Shapes of VirusShapes of Virus

2. Polyhedral 2. Polyhedral (Mumps)(Mumps)

Shapes of VirusShapes of Virus

3. Helical (Herpes)3. Helical (Herpes)

How does a DNA virus replicate?How does a DNA virus replicate?

DNA virus produces RNA (transciption)DNA virus produces RNA (transciption)RNA directs production of viral proteinsRNA directs production of viral proteins

OROR

Viral DNA combines with host cell’s DNA Viral DNA combines with host cell’s DNA (either plant or animal)(either plant or animal)

How does RNA virus replicate or How does RNA virus replicate or reproduce itself?reproduce itself?

Once inside the host, an RNA virus directs Once inside the host, an RNA virus directs the host cell to produce proteinsthe host cell to produce proteins

OROR

Viral RNA may make DNA Viral RNA may make DNA

Retrovirus Retrovirus

Virus that has RNA as its genetic materialVirus that has RNA as its genetic materialExample is HIVExample is HIV

BacteriophageBacteriophage

Virus that attacks a bacterial cellVirus that attacks a bacterial cell

Two types of infection:Two types of infection:

A.A. Lytic CycleLytic Cycle

B.B. Lysogenic CycleLysogenic Cycle

Lytic CycleLytic Cycle

Bacteriophage attaches to host cell and Bacteriophage attaches to host cell and injects its DNAinjects its DNA

Foreign DNA produces more proteins in Foreign DNA produces more proteins in the host cellthe host cell

Causes cell to lyse (or break open) and Causes cell to lyse (or break open) and the virus/phage is released into the host’s the virus/phage is released into the host’s bodybody

Lytic CycleLytic Cycle

Lysogenic CycleLysogenic Cycle

Phage injects DNA into the host cellPhage injects DNA into the host cell

Foreign/phage DNA integrates itself into a Foreign/phage DNA integrates itself into a chromosomechromosome

Bacteria reproducesBacteria reproduces

Lysogenic CycleLysogenic Cycle

Lytic vs.Lysogenic CycleLytic vs.Lysogenic Cycle