Transcript Chapter 13 Viruses

Chapter 13
viruses
Structure of viruses
•
•
•
•
•
Acellular
Either have DNA or RNA
Surrounded by a protein coat (capsid).
Envelope – proteins, carbohydrates, lipids.
Obligate intracellular parasites
Complex
virus
complex
Lytic
cycle
Lysogenized
cell
Lambda
phage
Biosynthesis
maturation
Daughter cells
descendants
Animal viruses
•
•
•
•
•
•
•
•
Papillomavirus (DNA virus)
Warts
Common warts – legs, hands
Direct contact
Treated with interferon.
Genital warts
Finger-like projections (cauliflower)
STD, cervical cancer
uncoating
RNA virus, poliovirus
• Fecal – oral route – contaminated food,
water
• Multiplies in the throat and small intestine
• CNS – multiplies in the nerve cells,
paralysis
• Polio vaccine
RNA dependent
RNA polymerase
RNA as a template
To make complementary strand of RNA
Retrovirus
•
•
•
•
•
RNA – genetic material
Reverse transcriptase
RNA as a template to make DNA
Capsid and envelope
Human immunodeficiency virus (HIV)
budding
Latent viral infection
• Herpes simplex virus
• Dormant – nerve cells, activated under
certain conditions – epithelial cells – cold
sores
• Herpes simplex virus 1 – oral herpes
• Infancy - direct contact
• Activated by fever, sunburn, stress
Herpes Simplex Virus 2
•
•
•
•
Genital herpes
Vesicles in the area
Burning, difficulty walking
acyclovir
Viruses and cancer
•
•
•
•
•
Nucleated cells have proto-oncogenes
Control (regulate) cell growth
Code for proteins – regulate cell growth
Mutation – abnormal proteins
Loss of control – uncontrolled proliferation
of the cell with mutation - cancer
Mutations
•
•
•
•
•
•
Chemicals
UV light
Viruses
Epstein-Barr virus – DNA virus
Dormant in some B lymphocytes
Transmitted in saliva – infectious
mononucleosis
Epstein-Barr virus
•
•
•
•
DNA virus
Dormant in some B-lymphocytes
Transmitted in saliva
Infectious mononucleosis
Burkitt’s Lymphoma
• Common childhood cancer in Africa
• Average age 7 – malaria is common
• EBV and Plasmodium cause mutation in
c-myc gene – proto-oncogene
• Loss of control of cell growth
• Uncontrolled proliferation
• Leads to cancer – jaw bones
Human T cell leukemia virus
•
•
•
•
T cell leukemia – retrovirus
Average age 45
Transmitted by sexual contact
Mutation increases the production of the T
cell growth factor.
• Proliferation of T cells
• Japan, Caribbean – multistep process
Prions
• Proteinaceous infectious particles –
proteins
• Scrapie – sheep
• Scrape themselves against fences
• Become paralyzed and die
• Mad cow disease – bovine spongiform
encephalopathy (BSE) – sponge like
degeneration of the brain.
• Shake, shiver
Creutzfeldt –jakob disease
• Occurs in certain families – hereditary
• Transmitted by contaminated hamburgers
• Dementia – die within a year
viroids
•
•
•
•
•
Naked piece of RNA
Plant pathogen
Potato spindle tuber viroid
Damage to potato plants
Evolved from introns