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