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