Bio chapter 26

Flashcards covering the anatomy, diversity, replication, and classification of viruses based on their structural components, genetic material, and interaction with host cells.

Genome

The genetic material of a virus, which can be either RNA or DNA.

Capsid

A protein sheath that surrounds and protects the viral genome.

Nucleocapsid

A capsid that is very tightly and closely associated with the viral genome.

Helical Capsid

A winding, staircase-like capsid shape, commonly seen in plant viruses like the Tobacco Mosaic Virus.

Icosahedral Capsid

A capsid shape composed of 20 triangular facets, characteristic of most animal viruses.

Bacteriophage

A bacterial virus exhibiting bihel symmetry, with an icosahedral head and a helical tail.

Enveloped Virus

A virus whose capsid is contained within an outer, flexible envelope (e.g., Influenza, Rabies).

Antigens

Recognition molecules found on the surface of cells and viral envelopes, unique to individuals or viruses, used by the immune system for identification.

Obligate Intracellular Parasites

Viruses, defined by their inability to replicate or carry out metabolic activity without infecting and hijacking a host cell.

Host Range

The specific group or category of organisms (or cells) that a particular virus can infect.

Tissue Tropism

The affinity of a virus for certain specific cell types within a multicellular host (e.g., Hepatitis B targets liver cells).

Ribosomes

Cellular structures responsible for protein synthesis; viruses lack the genes to produce them and rely on host cell ribosomes.

Reverse Transcriptase

A specific enzyme carried by some viruses (e.g., HIV) that synthesizes DNA from an RNA template, a process that is not natively performed by host cells.

Naked Viruses

Viruses that do not possess an outer envelope, typically exhibiting either a filamentous or icosahedral shape (e.g., Poliovirus).

Bihel Symmetry

A type of structural symmetry found in complex viruses like bacteriophages, combining both helical and icosahedral forms.

Latent Infection

A non-virile stage where a virus remains dormant within the body, potentially reactivating later to cause disease (e.g., Varicella Zoster virus causing shingles).

Viral RNA Polymerase

An enzyme essential for RNA viruses to replicate their RNA genomes from an RNA template, known for its high error-proneness.

RNA Virus Mutation Rates

High rates of genetic change in RNA viruses due to the error-prone nature of viral RNA polymerase, leading to the rapid emergence of new strains (e.g., Influenza, COVID-19).

Memory T Cells

Specialized immune cells that 'remember' specific pathogens from previous exposures, enabling a faster and more effective immune response upon subsequent encounters.

Segmented Genome

A viral genome that is divided into several separate pieces of nucleic acid rather than existing as a single molecule (e.g., Influenza virus).

Baltimore Classification

A commonly accepted system for classifying viruses based on their genome expression strategies.