http://www.youtube.com/watch?v=Rpj0emEGShQ

Virus Video

Viruses & Bacteria can cause infection

• Pathogen - Any disease-causing agent

viruses50-200 nm

prokaryotics cells200-10,000 nm

prion2-10 nm

viroids5-150 nm

eukaryotics cells10,000-100,000 nm

100 nm

1 nanometer (nm) = one billionth of a meter

Virus

• 2 basic parts:– protein coat. – Contains DNA or RNA

• non-living pathogen

• Viruses have a simple structure.

capsid nucleic acid

lipidenvelope

surfaceproteins

capsid

nucleic acid

lipid envelope

Surface proteins capsidsurfaceproteins

nucleic acid

helical(rabies)

polyhedral(foot-and-mouth

disease)

enveloped(influenza)

All viruses have two main parts:

1. DNA or RNA – genetic info

2. Capsid – a protein coat

Bacteriophages: viruses that infect bacteria.

capsid

DNA

tail sheath

tail fiber

• Viruses enter cells in various ways.

colored SEM; magnifications:large photo 25,000; inset 38,000x

– bacteriophages pierce host cells

Virus inserting it’s DNA into a bacterial cell.

Viral Replication Picture

http://glencoe.mcgraw-hill.com/sites/9834092339/student_view0/chapter28/life_cycle_of_t2_phage.html

http://www.mcgrawhill.ca/school/schoolGraphics/biology2_1.mpg

– Endocytosis (pulled into cell)

• Viruses enter cells in various ways.

– fuse with membrane

• Viruses enter cells in various ways.

Are viruses alive???Viruses contain DNA/RNA, proteins, and they reproduce…

NO.They contain no nucleus, cytoplasm, organelles or cell membrane; they cannot carry out cell functions, and they can only “reproduce” when an infected cell builds new viruses.

Grouping Viruses

• Grouped according to:– Presence of Capsid and envelope – shape– RNA or DNA, single or double stranded – structure

Viral Group Nucleic Acid Shape and Structure Example

Papovaviruses DNA Icosahedral, non-env. Warts, cancer

Adenoviruses DNA Icosahedral, non-env. Resp. & intestinal infections

Herpesviruses DNA Icosahedral, enveloped Herpes simplex, chicken pox, mono, shingles

Poxviruses DNA Complex brick, enveloped Small pox, cow pox

Picornaviruses RNA Icosahedral, non-env. Polio, hepatitis, cancer

Myxoviruses RNA Helical, enveloped Influenza A, B, C

Rhabdoviruses RNA Helical, enveloped Rabies

Retroviruses RNA Icosahedral, enveloped AIDS, cancer

Treatment and Prevention

Vaccines – creates antibodies

Anti-viral drugs: interfere with viral DNA/RNA synthesis

Inactivated- the virus is “dead”; cannot replicate

Attenuated- the virus has been genetically altered; still functional,

but won’t cause disease

Attenuated tend to be more effective vaccines

Some Pictures are Graphic

The Lysogenic CycleWhen viruses remain inactive within host cells for days, months or years.

•Viral DNA inserted directly into the host DNA.•Viral DNA copied with host DNA during replication•Viral DNA passed on to daughter cells during mitosis•Remains dormant (no viral proteins are produced) until some “triggering event”

Examples: Chickenpox and Shingles; HIV

Stress UV light

chemicals

heat

???

POXVIRUSESSmall Pox

BACK

PICORNAVIRUSES - Polio

BACK

Destroys the motor neurons that are

producing the virus. The result is a loss of

muscle control including the diaphragm. The iron lung changes the

pressure to pump air in and out of the lungs.

U.S. President

Franklin Delano Roosevelt

MYXOVIRUSESFlu Virus

BACK

RHABDOVIRUSESRabies

BACK

RETROVIRUSES

Herpes

HPV Tree man

Ebola

Syphilis

• Sketch & Label the following:

T4 Bacteriophages

capsid

DNA

tail sheath

tail fiber