Bio 122- Viruses (Exam 2)

Characteristics of life

• Organization

• Energy processing

• Response to Stimulus

• Evolve

• Growth*

• Reproduction*

*Viruses do not grow or reproduce their own cells, so they

Somewhere between living organism and non-living chemical compound

What is a Virus

has a _

is smaller than a ____

genome, ribosome 

Virus

Can be

DNA, single stranded RNA, or double stranded RNA

smallest viruses are

20 nm in diameter

virsus can _____________, smallest cells cannot

aggregate in crystals

virus can only reproduce in 

host cell

Viruses are

infectious particles

virus has

Nucleic acid

in a protein coat

virus 

Some cases have

a membranous envelope

Viral Shape

• Protein shell around virus is a

Capsid

Viral Shape

Made of

capsomeres

Viral Shape

Usually

rod-shaped, polyhedral, or more complex (T4)

• Recognition spike

protein to bind to host

Virulence

• The severity of a disease or poison

Virulence

Ability to

damage host

Virulence

Determined by

virulence factors

Bacteriophage—

virus that infects bacterium

Once bacterium is infected, it undergoes one of two life cycles:

-Lytic cycle

-Lysogenic cycle

• Every bacteriophage can undergo

lytic cycle

Lysogenic cycle can be a

long detour

Lytic cycle

phage reproductive cycle that ends in death of the host cell

• Lytic cycle uses

Bacterium

lyses

• Lytic cycle—

Virulent phage

phage that only reproduces with lytic cycle

Bacteria have their own

defenses

Lysogenic cycle—

replicates phage genome, doesn’t kill cell

Prophage

viral DNA copied in host cell

Classes of Viruses

• dsDNA

• ssDNA

• dsRNA

• ssRNA

Classes of Viruses

• ssRNA

serves as mRNA

Classes of Viruses

• ssRNA

– template for RNA synthesis

Classes of Viruses

• ssRNA

Template for DNA synthesis

Herpesvirus

dsDNA

other viruses like herpesvirus

• Adenovirus

• Papillomavirus

• Smallpox, cowpox, monkeypox

Parvovirus

• ssDNA

• Fifth disease

• Slapped-cheek disease

Rotavirus

• dsRNA

• Colorado Tick Fever virus

Polio(Poliovirus)

is how many RNA strands

Single-strand RNA

when was u.s. polio free

1979

Jonas Salk

developed the first successful polio vaccine

Jonas Salk’s polio vaccine 

Inactivated poliovirus

– Did not patent it

• Albert Sagan

—oral polio vaccine

• Albert Sagan

—oral polio vaccine

– Live, attenuated poli

Hilary Koprowski

—live polio vaccine, rabies, blamed for AIDS and cleared of it

polio

Now

NY SoE because of new cases

• No cure

Polio

current vax rates

79 percent

ssRNA template for RNA Synthesis

Ebola

Influenza

Measles

Mumps Rabies

Retrovirus

RNA genome is converted to DNA prior to viral reproduction

Retrovirus

viruses:

HIV, AIDS, RNA tumor viruses (leukeumia)

retrovirus uses

• ssRNAtemplate for DNA synthesis

Emerging Viruses

Rapidly come to the attention of scientists

Emerging Viruses

How do new viruses emerge?

Mutations of existing viruses • Rapid range expansion • Few antivirals, rapid spread

Prion

infectious protein

Prions

Kuru

eliminating cannibalism reduced prevalance

Prions

Misshapen_______that is Incurable

normal brain proteins

Prions is

Mad Cow, Creutzfeldt Jakob disease

• CWD

Viroid

small, circular RNA molecules

Viroids

• Disease in

plants

Viroids

Do not encode proteins,

but can replicate by using host enzymes

Viroids

_____ viroid

Potato spindle tuber

Viroids

_________viroid

Peach latent mosaic