Viruses

Dead or alive?

Viral structure

Viruses are not cells.

Basic structure:– Protein coat– Nucleic acid core

(RNA or DNA)-controls production of new viruses

Virus Categories

DNA viruses – stable, do not mutate rapidly– Single-stranded or double-stranded– Smallpox, Hepatitis B

RNA viruses – mutate rapidly, unstable– Single-stranded or double-stranded– HIV, Rhinovirus

Are viruses alive?

Only 1 characteristic of life: reproduction Can only reproduce inside another living

cell= host cell Host Cell: provides a home and or food

for a virus…..host harmed by virus Process or reproduction = lytic cycle

Lytic Cycle

Virus attaches to host cell’s membrane and injects its nucleic acid into the host cell.

The viral nucleic acid takes over protein synthesis, creating new viruses.

The host cell bursts, lyses, releasing the newly formed viruses.

Release

Before attachment

Attachment

Penetration and uncoating

ReplicationAssembly

VIRUS AND HUMANS

Cause a large number of human diseases– Ex. Colds, warts, AIDS, measles, flu, small

pox, mumps, hepatitis

VIRUS AND HUMANS

Can be helpful to humans– Vaccines– Germ Warfare– Change genetic material

VIRUS AND HUMANS

Vaccines: weakened virus that doctors inject into us so our body makes antibodies (fight disease)– Ex. Flu shot

After a person has a virus, they produce antibodies to fight the disease, so they will never get disease again– Ex. Chicken pox

VIRUS AND HUMANS

Germ warfare: use viruses to control pests. – Ex. Rabbits in Australia

Change genetic material– Scientist have learned to put genetic

material into viruses– Hopefully, they’ll be able to use viruses to

replace disease causing DNA in humans