Virology Fundamentals – Lecture Review

30 vocabulary flashcards summarise key virology terms, structures, replication strategies, notable viruses, and bacteriophage concepts from the lecture notes.

Virus

An obligate intracellular parasite composed of nucleic acid (DNA or RNA) enclosed in a protein coat; metabolically inert outside host cells and not considered living.

Virion

Complete extracellular virus particle, consisting of nucleic acid surrounded by a protein capsid (and, in some viruses, an envelope).

Capsid

Protective protein coat surrounding viral nucleic acid; made of self-assembling capsomere proteins.

Nucleocapsid

The combined structure of the viral genome plus its surrounding capsid.

Envelope (viral)

Lipid-protein membrane derived from host cell that surrounds some viruses; often contains glycoprotein spikes for host recognition.

Naked Virus

Virus lacking an envelope; composed only of nucleocapsid.

Helical Capsid

Capsid in which proteins are arranged in a rod-like spiral around the genome, forming hollow tubes.

Icosahedral Capsid

Capsid with 20 equilateral triangular faces and 12 vertices; capsomeres form triangular units.

Complex Virus

Virus whose structure is neither purely helical nor icosahedral (e.g., bacteriophage with head-tail morphology).

Host Range

Spectrum of host species or cell types a virus can infect, determined by attachment receptors, intracellular machinery, and release mechanisms.

Attachment (Adsorption)

Initial step of infection where viral proteins bind specific receptors on the host cell surface.

Reverse Transcriptase

Viral enzyme that synthesises complementary DNA (cDNA) from an RNA template; essential for retrovirus replication.

RNA-dependent RNA Polymerase

Enzyme that copies viral RNA into RNA; used by RNA viruses such as coronaviruses for genome replication.

Retrovirus

RNA virus (e.g., HIV) that uses reverse transcriptase to integrate a DNA copy of its genome into the host chromosome.

Prophage

Latent form of bacteriophage genome integrated into bacterial DNA during the lysogenic cycle.

Lytic Cycle

Bacteriophage replication pathway involving immediate production of new phages and lysis of the host cell.

Lysogenic Cycle

Bacteriophage pathway where phage DNA integrates into host genome as a prophage, replicating silently until induced to enter the lytic cycle.

Transduction

Process by which bacteriophages transfer bacterial DNA from one cell to another during viral assembly.

Phage Conversion

Acquisition of new traits by bacteria due to expression of prophage genes (e.g., cholera toxin production by Vibrio cholerae).

Smallpox (Variola)

Eradicated viral disease responsible for 300–500 million deaths in the 20th century; last natural case in 1977.

Influenza A & B

Orthomyxoviruses that cause seasonal flu epidemics; rapid antigenic change necessitates twice-yearly vaccine updates.

HIV (Human Immunodeficiency Virus)

Retrovirus infecting CD4⁺ cells; causes AIDS; ~38 million people living with infection (2022).

Ebolavirus

Filovirus causing severe hemorrhagic fever; West African epidemic (2014-15) had ~55 % mortality.

Zika Virus

Mosquito-borne flavivirus linked to microcephaly in fetuses; can be sexually transmitted.

SARS-CoV-2

Coronavirus responsible for COVID-19 pandemic (>700 million cases, >7 million deaths by 2024).

Mutation of Viral Glycoproteins

Adaptive changes in surface proteins that enable entry into new host cell types and evasion of immunity.

Replication (viral)

Stage where numerous copies of the viral genome are synthesised within the host cell.

Assembly

Self-organisation of capsid proteins around newly replicated genomes to form mature virions.

Budding

Mechanism by which enveloped viruses exit a host cell, acquiring envelope from the plasma membrane.

Obligate Intracellular Parasite

Organism (e.g., virus) that can reproduce only inside a living host cell, relying on host machinery for replication.