Chapter 6 Viruses Virus: a noncellular genetic element that enlists a cell for its own replication, it has an extracellular state a virus particle containing nucleic acid surrounded by protein and other macromolecular components is called virion Viruses have a heavy dependence on host-cell structural and metabolic components Viruses can confer important new properties on their host cell
Chapter 6 Viruses Virus : a noncellular genetic element that enlists a cell for its own replication, it has an extracellular state. A virus particle containing nucleic acid surrounded by protein and other macromolecular components is called virion. Viruses have a heavy dependence on host-cell structural and metabolic components. Viruses can confer important new properties on their host cell
Classification of viruses Viruses can have either DNA or RNA as genetic material According to hosts viruses infect Bacterial viruses( Bacteriophage or噬菌体) Animal viruses(well studied) Plant viruses (less studied) According to nucleic acid structures DNA viruses(ss dna, ds dna) RNA viruses(ss rna, ds rna) RNA DNA VIruses(ss rna, ds dna)
Classification of Viruses Viruses can have either DNA or RNA as genetic material According to hosts viruses infect: – Bacterial viruses (Bacteriophage or 噬菌体） – Animal viruses (well studied) – Plant viruses (less studied) According to nucleic acid structures: – DNA viruses (ss DNA, ds DNA) – RNA viruses (ss RNA, ds RNA) – RNA DNA viruses (ss RNA, ds DNA)
Nature of the virion Virus size: 20 nm to 300 nm argest virus: Smallpox(天花病毒)is200nm Smallest virus;: Polio virus(脊髓灰质炎病毒)is28nm Virus genome: Smaller than those of cells, the largest known viral genome: vaccinIa(牛痘) is only 190 KB Bacterial genomes: 1000-9000 KB
Nature of the virion Virus Size: 20 nm to 300 nm Largest virus: Smallpox (天花病毒) is 200 nm Smallest virus: Polio virus (脊髄灰质炎病毒) is 28 nm Virus genome: Smaller than those of cells, the largest known viral genome: vaccinia (牛痘) is only 190 KB. Bacterial genomes: 1000-9000 KB
Virus structure Nucleo Envelope apsIa Capsomeres Capsid Nucleic Nucleic acid Capsid (composed of capso meres) Naked virus Enveloped virus Viruses consist of nucleic acids, capsid, and/or envelope
Virus Structure Viruses consist of nucleic acids, capsid, and/or envelope
Virus Symmetry Helical symmetry: Tobacco mosaic virus(TMv) Icosahedron: The most efficient arrangement for subunits in a closed shell Enveloped viruses: envelope consists of lipid bilayer with glycoproteins embedded in it. Its symmetry refers to its nucleocapside. Complex viruses: T4 bacteriophage
Virus Symmetry Helical symmetry: Tobacco mosaic virus (TMV). Icosahedron: The most efficient arrangement for subunits in a closed shell. Enveloped viruses: envelope consists of lipid bilayer with glycoproteins embedded in it. Its symmetry refers to its nucleocapside. Complex viruses: T4 bacteriophage