BIO by M Tahir ( Lecturer Al Azhar )

Ebola virus has a long, filamentous appearance and belongs to the Filoviridae family.

The icosahedral design provides great structural strength while requiring relatively few capsid proteins.

Viruses can infect only cells possessing compatible receptors that allow attachment and entry. This determines host specificity and tissue tropism.

Mumps virus belongs to the Paramyxoviridae family and possesses a negative-sense single-stranded RNA genome.

RNA polymerases lack efficient proofreading mechanisms, resulting in frequent mutations and rapid viral evolution.

Adenovirus lacks a lipid envelope and possesses an icosahedral protein capsid enclosing double-stranded DNA.

Zoonotic viruses naturally circulate among animals but can also infect humans. Rabies virus and some coronaviruses are examples.

SARS-CoV-2 is an enveloped positive-sense single-stranded RNA virus belonging to the Coronaviridae family.

Lipid envelopes are easily disrupted by detergents, alcohol, and drying, resulting in loss of infectivity.

The contractile tail sheath helps inject viral DNA through the bacterial cell wall into the host cytoplasm.

Most plant viruses enter through wounds or are transmitted by insect vectors such as aphids because intact plant cell walls prevent direct entry.

Rabies virus travels through peripheral nerves to the central nervous system, causing fatal encephalitis if untreated.

Retroviruses possess single-stranded RNA and use reverse transcriptase to synthesize DNA before replication. HIV is the best-known example.

Hepatitis C virus belongs to the Flaviviridae family and contains a positive-sense ssRNA genome.

Complex viruses, such as bacteriophage T4, possess an icosahedral head, helical tail, and specialized attachment structures.

HIV infects human immune cells and therefore belongs to the animal viruses.

Enveloped viruses commonly enter cells by membrane fusion or receptor-mediated endocytosis.

Measles virus belongs to the Paramyxoviridae family and causes a highly contagious viral disease characterized by fever and rash.

Herpesviruses possess large linear double-stranded DNA genomes enclosed within an icosahedral capsid.