VirusesChapter 24

StandardsStandard 1: Cells CLE 3216.1.6 Describe the relationship between

bacteria, protists, and viruses and their host cells

Prokaryotes

Viruses NOT living (don’t meet all requirements)

Ex: Don’t grow and develop Needs a host to survive Cannot carry out cellular functions

Core of DNA or RNA surrounded by protein coat

Reproduce only by infecting living cells

Viral DiseasesViruses that cause disease attack and

destroy cellsCannot be treated with antibiotics

(maybe over the counter medicines)Vaccines work if used before virus is

contracted

Common Viral Diseases

Common coldFluAIDSChicken Pox/ShinglesHepatitis BWest Nile Virus

Virus Structure Core filled with genetic

material inside Capsid =protein coat Proteins attach to cell

“tricking” it into letting the virus in

Viral genes are copied Host cell dies Bacterophage = virus

that only infects bacteria

Classification of Viruses

Have RNA vs DNA as their genomeDouble stranded vs Single strandedLinear vs Circular

Viral Infection 2 viral infection processes:1. Lytic infection - host cell bursts2. Lysogenic infection - virus remains

inactive inside of host for periods of time

Lytic Infection Virus DNA is injected

into host cell Cell begins to copy

virus DNA, then make virus proteins

Virus proteins break down host cell and uses it to copy more viruses

Cell finally bursts (lyses)

Lysogenic Infection Virus DNA is injected

into host cell’s DNA DNA is replicated with

included viral DNA Cell does not lyse -

virus remains inactive for period of time

Then enters lytic cycle when inactivation is over

Retrovirus Virus with RNA as

genetic material Retro = backwards Copies RNA into

DNA instead of DNA to RNA

Ex: AIDS

Emerging DiseaseIllness caused by new or reappearing

agents that typically exist in animal populations

Ex: Ebolo virus

Viroids and PrionsViroids: smallest known particles

known to replicate - Infect plants

Prions: Infectious protein particles - causes degenerative brain diseases Ex: Mad cow disease