Viruses, Viroids, Prions So you thought infectious bacteria were bad?

What is a Virus? A virus, as Nobel laureate Peter Medawar described it, "is a piece of bad news wrapped in a protein.”

Virus Body Genetic material is DNA or RNA Coat is protein Complex virus (bacteriophage) Polyhedral virus Rod-shaped virus head sheath tail fiber

Types of Virus Many shapes DNA or RNA Capsid - protein coating Identity proteins

DNA Viruses virology.net/Big_Virology/BVDNAadeno.html Adenovirus (colds and pink eye) Herpes Simplex Virus -I on human lymphocyte

RNA Viruses Corona Virus SARS Common Cold Virus Influenza virus

Virus injects genetic material Production of viral components Assembly Lysis Lytic Pathway Obligate intracellular parasites

Lysogenic Pathway Latent period extends the cycle Viral DNA becomes part of host chromosome for a time Viral material integrated Viral material passed on Stimulus may cause cell to enter lytic pathway

Lytic Versus Lysogenic Lytic - virus immediately has cell reproduce it and then bursts cell. Lysogenic - virus lies dorment as cell lives its life and does mitosis, then enters lytic cycle.

Bacteriophage Life Cycle

Lysogenic lifecycle of phages

Retro-virus RNA converted to DNA inside host cell by reverse- transcriptase. Example: Viral RNA - UUA GGC reverse transcribed to DNA - AAT CCG DNA inserted into cells DNA

HIV Structure RNA Capsid Lipid Coat Surface Proteins Proteins Lipid coat RNA Capsid

Enveloped Virus (HIV)

HIV Life Cycle A. HIV attaches to cell- surface receptors on Helper T cell. B. Fuses with cell membrane and RNA enters cell. C. RNA transported to nucleus. D. Converted into DNA reverse transcriptase (red dot).

HIV Life Cycle E. DNA moves into nucleus. F. Viral DNA integrated into cellular DNA. G. Two types of viral RNA made by transcription. H. Shorter RNA for making viral proteins.

HIV Life Cycle I. Viral proteins J. Full-length genomic RNA K. Genomic RNA L. New virus assembled M. Mature virus is released

HIV/AIDS Can be dormant for up to 10 years. Person is a carrier/vector for that time.

AIDS Symptoms Swollen lymph nodes Loss of appetite and weight Fever Rashes Night sweats Fatigue

AIDS Because HIV destroys Helpter T Cells it cripples the immune system. AIDS is when someone with HIV starts to get other illnesses because of weak immunity.

HIV Transmission Blood Body Fluids Direct Contact Vector

Viroids Just a piece of RNA Many plant diseases Human - Hepatitis D Complex cycle including “another” virus – Hepatitis B. Potato spindle tuber viroid

Prions Misfolded proteins infectious make plaques (clumps) & holes in brain as neurons die Creutzfeldt-Jakob disease “mad cow” disease