C.2 Structure and Types of Viruses

Viral Genome

The nucleic acid (DNA or RNA) inside a virus, which can be double-stranded DNA (deoxyribose) or single-stranded RNA (ribose). within capsid.

Capsid

The protein shell surrounding the viral genome; determines the virus’s shape and ability to infect cells.

Viral Infection

Occurs when capsid proteins interact with a host cell’s membrane to deliver the viral genome into the cell.

Viral Specificity

The ability of a virus to infect only specific host cells (e.g., HIV targets white blood cells; rabies targets cells of several animals).

Viral Envelope

A lipid/protein layer outside some viruses that camouflages them, helping avoid detection by the host immune system.

Bacteriophage

A complex virus that infects and kills bacteria; has a DNA genome.

Spherical Viruses

• Poxviruses: Cause skin eruptions (smallpox, cowpox).

• Chickenpox virus (Zoster virus): Not a true poxvirus.

• Coronaviruses: Enveloped RNA viruses causing respiratory infections; spikes on capsid create a crown-like appearance (“corona”).

• Rhinoviruses: Cause respiratory infections like the common cold.