Viruses, Viroids, and Prions

These flashcards cover key concepts relating to viruses, viroids, and prions, including their structures, functions, classifications, and clinical significance.

What are the two types of nucleic acid contained in viruses?

Viruses contain either DNA or RNA, but never both.

What distinguishes viruses from bacteria?

Viruses are obligate intracellular parasites and cannot multiply outside living host cells, whereas bacteria can live and reproduce independently.

What is the term for the spectrum of host cells that a virus can infect?

Host range.

In what year was the tobacco mosaic virus first isolated, and by whom?

The tobacco mosaic virus was first isolated in 1935 by Wendell Stanley.

What is the role of viral nucleic acids once a virus is inside a host cell?

Viral nucleic acids become active and direct the synthesis of new viral components using the host cell's machinery.

Define a virion.

A virion is a complete, fully developed, infectious viral particle composed of nucleic acid surrounded by a protein coat.

What are the characteristic structural components of a virus?

Viruses contain a nucleic acid (DNA or RNA), a protein coat (capsid), and sometimes an envelope made of lipids, proteins, and carbohydrates.

What is the difference between lytic and lysogenic cycles in bacteriophages?

The lytic cycle results in the death of the host cell, whereas the lysogenic cycle involves the integration of viral DNA into the host cell's DNA without killing the host.

What are spikes in viruses?

Spikes are carbohydrate-protein complexes projected from the surface of the viral envelope that help the virus attach to host cells.

Explain the significance of reverse transcriptase in retroviruses.

Reverse transcriptase allows retroviruses to convert their RNA genome into DNA, which can be integrated into the host's genome.

What causes the variability in symptoms between different viral infections?

Different viral infections cause varying symptoms due to the virus type, host immune response, and specific cell types infected.

How are plant viruses typically transmitted?

Plant viruses are often transmitted through injuries in plant cell walls or by vectors such as insects.

What is an oncogene?

An oncogene is a gene that has the potential to cause cancer; it can be derived from cellular genes and be part of the viral genome.

What are viroids?

Viroids are short pieces of naked RNA that can cause disease in plants and lack a protein coat.

How do prions differ from viruses?

Prions are infectious proteins that can cause disease by inducing abnormal folding of normal proteins, whereas viruses contain nucleic acids (DNA or RNA) and have a protein coat.

What is hepatitis A and how is it transmitted?

Hepatitis A is a nonenveloped + stranded RNA virus that is transmitted via the fecal-oral route.

What role do bacteriophages play in medical research?

Bacteriophages are important in medical research as they provide insights into viral replication and may be used in phage therapy to treat bacterial infections.