Transcript Viruses

Viruses
Chapter 24
Standards
Standard 1: Cells

CLE 3216.1.6
Describe the relationship between
bacteria, protists, and viruses and their
host cells
Prokaryotes
Viruses
 NOT living (don’t meet all requirements)
 Ex: Don’t grow and develop
 Needs a host to survive
 Cannot carry out cellular functions
 Core of DNA or RNA surrounded by protein coat
 Reproduce only by infecting living cells
Viral Diseases
Viruses that cause disease attack and
destroy cells
Cannot be treated with antibiotics (maybe
over the counter medicines)
Vaccines work if used before virus is
contracted
Common Viral Diseases
Common cold
Flu
AIDS
Chicken Pox/Shingles
Hepatitis B
West Nile Virus
Virus Structure
 Core filled with genetic
material inside
 Capsid =protein coat
 Proteins attach to cell
“tricking” it into letting the
virus in
 Viral genes are copied
 Host cell dies
 Bacterophage = virus that
only infects bacteria
Classification of Viruses
Have RNA vs DNA as their genome
Double stranded vs Single stranded
Linear vs Circular
Viral Infection
 2 viral infection processes:
1. Lytic infection - host cell bursts
2. Lysogenic infection - virus remains
inactive inside of host for periods of time
Lytic Infection
 Virus DNA is injected
into host cell
 Cell begins to copy
virus DNA, then make
virus proteins
 Virus proteins break
down host cell and
uses it to copy more
viruses
 Cell finally bursts
(lyses)
Lysogenic Infection
 Virus DNA is injected
into host cell’s DNA
 DNA is replicated with
included viral DNA
 Cell does not lyse virus remains inactive
for period of time
 Then enters lytic cycle
when inactivation is
over
Retrovirus
 Virus with RNA as
genetic material
 Retro = backwards
 Copies RNA into DNA
instead of DNA to RNA
 Ex: AIDS
Emerging Disease
Illness caused by new or reappearing agents
that typically exist in animal populations
Ex: Ebolo virus
Viroids and Prions
Viroids: smallest known particles known to
replicate
- Infect plants
Prions: Infectious protein particles
- causes degenerative brain diseases
Ex: Mad cow disease