These classical scenarios give different timelines for the origin(s) of viruses and do not explain the provenance of the two key functional modules that are responsible, respectively, for viral genome replication and virion morphogenesis.
Traditionally, three scenarios for the origin of viruses have been considered: descent from primordial, precellular genetic elements, reductive evolution from cellular ancestors and escape of genes from cellular hosts, achieving partial replicative autonomy and becoming parasitic genetic elements. It is widely accepted that viruses are polyphyletic, but a consensus scenario for their ultimate origin is still lacking.
Viruses are ubiquitous parasites of cellular life and the most abundant biological entities on Earth.
0 kommentar(er)
