Download notes chap. 24 virsuses - Fort Thomas Independent Schools

Chap. 24:Viruses
Ex. Cold, polio, rabies, herpes,
AIDS, small pox, flu, cancers,
mono, chicken pox, HPV, Ebola,
SARS, West Nile, Mad-Cows
Disease, etc.
I. Terminology
Virology – study of viruses
Virulent – when a virus causes a disease
Temperate – when a virus doesn’t cause
disease right away (AIDS, cancer)
Obligate intracellular parasite – (virus)
must use a host for reproducing
Nanometer (nm) – measurement for virus.
4000 can fit within a typed “o”
- Viroid – smaller than a virus – contains
only a single strand of RNA
Prion – contains about 250 amino acids –
no nucleic acid. Causes long term
diseases like Kuru.
Bacteriophage – virus that attacks bacteria
(also called phages)
Oncogenes – genes that cause abnormal
cell growth (tumors, aka cancer)
II. Structure
- classified by either having DNA or RNA
not by binomial nomenclature.
-- RNA viruses contain reverse transcriptase an
enzyme that changes RNA to DNA – called
retroviruses.
III. Viral Cycles
1. Lysogenic Cycles
a. Tail fibers attach to cell
b. Nucleic acid injected into host
c. Nucleic acid attaches to host nucleic acid
to become a prophage
d. Doesn’t cause harm immediately but at
some point it can become the lytic cycle.
e. Causes transduction (spreading of new
DNA to another cell) ex. Cancers,cold
sores,shingles, AIDS
2. Lytic Cycle – immediate taking over of a
host cell.
a. Attachment – virus attaches tail fibers down
onto host cell membrane.
b. Entry – DNA/RNA is injected into cell.
c. Replication – viral DNA/RNA tells host cell to
make more viruses
d. Assembly – making of more viruses
e. Lysis (release) – host cell ruptures and
releases all viruses to go and infect new cells.
-- interferon – chemical released by host cell upon
rupture to signal neighboring cells of virus
IV. Transmitting of viruses
Vector – organism that transmits a virus –
usually an arthropod (insect) ex. Tick,
mosquito, flea
Viral reservoir – place where virus
originated
--- viruses are transmitted by : air,
exchange of body fluids, direct contact,
water
A. Viral Control
1. vaccination – given inactivated (dead or
diluted amount) or attenuated (genetically
altered) virus.
---- Result : Antibodies – made by body to
recognize and destroy virus
2. Antiviral drugs – drugs that interfere with
viral making. Ex. AZT for AIDS
*** Antibiotics do not work on viruses because they
are made to target the cell processes of a bacteria
Pandemic – when a disease spreads
across the world. Ex. AIDS
Endemic – disease isolated to a specifc
region. Ex. Ebola
Epidemic – rapid spreading of a disease
and affecting many. Ex. Influenza 1918