Acellular Life: Viruses, Prions, and Viroids

A set of fill-in-the-blank practice flashcards covering the history, structure, classification, and parasitic nature of viruses based on lecture notes.

The word virus is derived from a Latin word __________ meaning 'poison'.

venom

In $1884$, __________ found that the causative agents of rabies could pass through the porcelain filter.

Charles Chamberland

Iwanowsky in $1892$ extracted juice from tobacco leaves and passed it through a filter with pore sizes of __________ to investigate tobacco mosaic disease.

$$100-1000\,nm$$

In $1935$, __________ crystallized the infectious particle now known as tobacco mosaic virus (TMV).

W. M. Stanley

The study of viruses is known as __________.

virology

Viruses are considered __________ because they enter the cells of living organisms and cause disease, but cannot replicate independently.

intracellular obligate parasites

A complete infectious viral particle is referred to as a(n) __________.

virion

The core of a virus consists of the viral genome and various __________ that facilitate its mode of action.

enzymes

Retroviruses and hepatitis B virus utilize the enzyme __________ to convert single stranded RNA into double stranded DNA.

reverse transcriptase

The protein coat surrounding the viral core is called the __________.

capsid

A capsid is composed of identical repeating subunits called __________.

capsomeres

The herpes virus has a specific number of $162$ capsomeres, while the __________ that causes the common cold contains $252$ capsomeres.

adenovirus

Capsid symmetry is described as __________ when capsomeres are arranged in $20$ triangles, and helical when they form a hollow coil.

icosahedral

The __________ classification system categorizes viruses into seven groups based on their mode of replication and genome type.

Baltimore

A(n) __________ is a DNA virus characterized by a polyhedral head and a tail that attacks bacteria.

bacteriophage

In animals, the __________ causes cancer, while the Papovirus causes warts.

Rous sarcoma virus

The poliovirus is highly specific, reproducing only in spinal nerve cells, while __________ viruses infect only the cells lining the upper respiratory tract.

human cold

The __________ of a virus is determined by the specificity of attachment between viral protein spikes and host cell receptors.

host range

While the poliovirus has a narrow host range, the __________ virus has a broad range and can enter all mammalian cells.

rabies

Inside the host cell, the capsid protects the viral genome from __________, which are host enzymes that break down DNA or RNA.

nucleases

Outside the host body, viruses remain __________ as they have no metabolic activity of their own.

dormant

__________ viruses can survive for several days outside the host, whereas enveloped viruses survive for shorter periods.

Non-enveloped