Chapter 24: Viruses and Subviral Agents

virus

A(n) ________ is a very small infective agent that consists of a core of nucleic acid and is dependent on a living host.

Prions

________ cause fatal degenerative brain diseases, such as transmissible spongiform encephalopathies (TSEs)

HIV

Retroviruses, such as ________, use reverse transcriptase to transcribe their RNA genome into a DNA intermediate that becomes integrated into the host DNA.

Diseases

________ caused by DNA viruses include herpes, respiratory infections, and gastrointestinal disorders.

Lytic cycle

In a(n) ________, the virus destroys the host cell.

Viruses

________ may trace their origin to animal cells, plant cells, bacterial cells, or archaeal cells.

Temperate virus

A(n) ________ alternates between a lytic and a lysogenic cycle.

Lysogenic cycle

In a(n) ________, the genome of a temperate virus is replicated along with replication of the hosts DNA without causing death of the host cell.

complex cellular ancestors

The regressive, or reduction, hypothesis asserts that viruses are remnants of cellular organisms; they evolved from free- living, ________.

Virus

A(n) ________ is a subcellular particle consisting of a DNA or RNA genome surrounded by a protein coat, called a capsid.

Viruses

________ enter animal cells by membrane fusion or by endocytosis.

Viroid

A(n) ________ consists of a short strand of RNA with no protein coat.

Viruses

________ contain the nucleic acids necessary to make copies of themselves, but to reproduce they must invade living cells and commandeer their metabolic machinery.

viruses

In some ________ the capsid is surrounded by an outer envelope.

Viruses

________ are classified based on host range, the types of host species they can infect; the type of nucleic acid they contain; and whether the nucleic acid is single- stranded or double- stranded.

Viruses

________ may have initially existed as self- replicating units.

Viruses

________ can be spread among plants by insect vectors.

Viruses are classified based on host range, the types of host species they can infect; the type of nucleic acid they contain; and whether the nucleic acid is single-stranded or double

stranded