Download Viruses

Viruses
Classified as Non-living, so why do
we mention them in biology?
Viruses
From Latin for “poison”
Segments of nucleic acid (DNA or RNA)
contained in a protein coat (capsid); some
also have an envelope
Variety of shapes
Very small, about 1/10 size of most bacteria
NO cell membrane, nucleus, or organelles
Influenza Virus
Terms
Pathogen = agents that cause
disease, could be a virus, bacteria,
fungus, or protist
Vaccine = helps immune system
recognize and destroy virus or
bacteria
Phage = another word for virus
Viral Reproduction
Lytic Cycle = cell is destroyed,
ruptures (active stage)
Lysogenic Cycle = cell survives; viral
genes integrate into the host genes
and divide with the host (dormant
stage)
Alone, viruses do not use energy.
Viral Reproduction
Diseases Caused by Viruses
Bacteriophage = virus that infects bacteria (most
common is T4); sometimes used to benefit patients by
delivering missing genes (gene therapy)
Plant viruses – tulip break virus, TMV (tobacco mosaic
virus)
Animal viruses – HIV, colds, Ebola, Hepatitis A, B, C, D, E;
polio, herpes, influenza, mumps, rabies, SARS
Cancer-causing viruses – HepBV & HepCV (cause liver
CA), Epstein-Barr Virus (causes lymphoma); HPV (causes
cervical CA)
DNA vs. RNA Viruses
DNA Viruses are stable and rarely mutate; this is
why you only need to be vaccinated one time
Ex. Chickenpox virus
RNA Viruses are less stable and tend to mutate
frequently; this is why a new flu shot comes out
every year
Ex. Influenza virus
Which type is HIV?