Viruslar

Viruslar are small infectious agents that replicate only inside living cells. They are typically much smaller than bacteria and lack cellular structure, metabolism, and independent replication. To reproduce, viruslar must hijack the molecular machinery of host cells, turning them into virus-producing factories.

Structure and genome. Viruslar consist of genetic material—DNA or RNA—enclosed within a protective protein shell called a capsid. Some viruslar have an outer lipid envelope derived from host membranes and studded with surface proteins that determine host range and entry. The genome can be single- or double-stranded and may be linear or segmented; it can encode a few to hundreds of genes.

Life cycle. Most viruslar attach to specific receptors on a host cell, enter by fusion or endocytosis, release their genome, and use host or viral enzymes to replicate. New virions assemble and exit the cell, often causing cell damage or death. The replication strategy depends on whether the genome is DNA or RNA and whether it is positive-sense, negative-sense, or reverse-transcribing.

Classification and examples. Viruslar are classified by genome type, replication method, and structure, commonly organized into groups such as dsDNA, ssDNA, dsRNA, positive-sense RNA, negative-sense RNA, and reverse-transcribing viruses. Well-known families include Herpesviridae, Retroviridae, Flaviviridae, Orthomyxoviridae, and Coronaviridae, among others.

Impact and control. Viruslar are responsible for diverse diseases in humans, animals, and plants, but also play roles in ecosystems and biotechnology. Public health measures include vaccination, antiviral medications, and infection control. Detection relies on molecular methods (PCR), serology, and microscopy. Vaccines remain a primary preventive tool, while antiviral therapies target specific viral enzymes or processes.