virus video
TRANSCRIPT
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
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