Virus

Core concepts

A virus is a non-cellular particle which consists of a core of nucleic acid (DNA or RNA) surrounded by a protein coat (capsid). It is an infectious agent that is only capable of metabolism and reproduction within a living cell.

In order to reproduce, viruses must infect a host cell in one of two ways: through a lytic or a lysogenic cycle.

Key words

Virus capsidbacteriophage/phage lytic cyclelysogenic cycle virulent phagetemperate phage prophage/provirusRetrovirus reverse

transcriptaseViroid prionInterferon vaccine

Dmitri Iwanowskie and the TMV

Ukrainian biologist and founder of virology

Adolf Mayer suggested an infectious agent affecting tobaccos

Using the steps in the Koch’s postulate he was able to extract the tobacco mosaic virus

TMV

Virus structure

Virus

“Organisms at the edge of life”Have genes, evolve, reproduce(self-assembly)No cellular structure (unit of life)Do not have own metabolism (requires host)Need host cell to reproduceGoverned by natural selectionGives proof to chemosynthetic theory

Taxonomy

Order (-virales)Family (-viridae)

Subfamily (-virinae)Genus (-virus)

Species (-virus)

Classification

Genetic MaterialShapeSizePresence of envelopeSpecificityDisease type

Genetic material

DNA virusRNA virus

Also called retrovirus

If a virus has a single stranded genetic material it is more prone to mutation

Viral infection

Very SpecificBinds to surface receptors

Lytic Cycle

Lysogenic Cycle

Lytic and Lysogenic cycle

The retrovirus and HIV

Whys is a retrovirus very dangerous? Genetic stability- exists as a provirus High expression Flexible genome

Possible Origin of Virus

pieces of cellular DNA that became part of an infectious particle

although small and relatively simple, are not likely to have been the first living things on earth since they’re completely dependent on living cells

may have evolved from genetic material of living cells, and continue to evolve along with their host cells