Viruses

Viruses are very small

Anatomy of a Virus

Viral Genomes

Viruses may have • Double stranded DNA• Single stranded DNA• Double stranded RNA• Single stranded RNA

• Viruses are called either a DNA or RNA virus depending on their type of genome

Some Viruses Which Infect Humans Class of virus

(type of genome)Name of Virus Examples

Double stranded DNA Papovavirus

Herpesvirus

Papilloma (warts, cervical cancer)

Herpes simplex I (cold sores), Herpes simplex II (genital sores), Varicella zoster (chicken pox)

Single stranded DNA Parvovirus Rosoela

Double stranded RNA Reovirus Diarrhea, mild respiratory disease

Single stranded RNA PicornavirusTogavirusRhabdovirusParamyxovirusOrthomyxovirusRetrovirus

Rhinovirus (common cold)Rubella, Yellow Fever, EncephalitisRabiesMeasles, mumpsInfluenzaHIV (AIDS virus)

Virus Reproduction

• Do viruses haveo A nucleus?o Enzymes for metabolism? o Ribosomes for protein synthesis?

Viruses can reproduce only within a host cell

Virus Reproduction

The Lytic Cycle• Culminates in the

death of the host cell

The Lysogenic Cycle• Replication of the

viral genome without destroying the host cell