Viruses Biology 2 Mr. Beyer

Bacteriophage

What is a Virus? Non-cellular Particle (not made of cells) Genetic Material will be one or the other DNA RNA (retrovirus) makes DNA from RNA instead of process where DNA is made from RNA Protein Coat (covering around nucleic acid) No independent cellular reproduction No cellular independent cellular metabolic capabilities

Two Types of Viral Infections Lytic Cycle The virus kills the host cell immediately creating symptoms of the disease…fever, pain, swelling, sores…. Lysogenic Cycle Virus enters the host cell and remains dormant Formation of a provirus (the virus DNA has attached itself to the host DNA)

Lytic Cycle Attachment (Adsorption)-Attaches to the host cell receptor sites Entry-The virus injects is Nucleic Acid (DNA or RNA) into the host cell Provirus Formation-Virus nucleic acid attaches to host cell nucleic acid (formation of provirus) Replication-Host cell replicates its DNA with virus DNA attached. The host cell unwittingly makes virus parts. Assembly- Virus parts are assembled inside the host cell. Lysis-Viruses fill the host cell, release an enzyme that breaks open the cell membrane and releases the viruses, killing the host cell…….symptoms appear in organism

Lysogenic Cycle Attachment (Adsorption)-Attaches to the host cell receptor sites Entry-The virus injects is Nucleic Acid (DNA or RNA) into the host cell Provirus Formation-Virus nucleic acid attaches to host cell nucleic acid (formation of provirus) Cell Division-Cells divide, replicating viral DNA with host cell DNA. Replication-Host cell replicates its DNA with virus DNA attached. The host cell unwittingly replicating viral nucleic acid. DORMANCY…… few or no symptoms or the disease….. virus remains dormant for a period of time…..eventually the virus will complete its life cycle and continue to the lytic cycle, killing the host cell

Lytic Cycle

Virulence A virus’s ability to cause disease Common cold (low virulence) HIV (high virulence)