viroid

[ vahy-roid ]

noun

1. an infectious agent of plants similar to a virus but consisting of only a short, single strand of RNA without a protein coat.

viroid

/ ˈvaɪrɔɪd /

noun

1. any of various infective RNA particles, smaller than a virus and known to cause some plant diseases

viroid

/ vī′roid′ /

1. An infectious agent that consists solely of a single strand of RNA and causes disease in certain plants. Viroids lack the protein coat (known as a capsid) of viruses and are the smallest known infectious agents. Containing only about 250 to 375 base pairs, they are much smaller than the smallest genomes of viruses and have no genes for encoding proteins. After invading a host cell, viroids are thought to mimic the cell's DNA, so that the cell's RNA polymerase replicates them in the nucleus. Viroids are believed to cause disease by interfering with the host cell's gene regulation. They are destructive to many important commercial plants, including potatoes, tomatoes, cucumbers, coconuts, and chrysanthemums.

Word History and Origins

Origin of viroid¹

First recorded in 1946; vir(us) + -oid

Word History and Origins

Origin of viroid¹

C20: from vir ( us ) + -oid

Example Sentences

At the time, scientists thought that something as small as viroids, which are one eightieth the size of many viruses, were too minuscule to cause an infection.

From New York Times

A viroid functions in a manner similar to that of a virus, invading a cell and making it reproduce the viroid’s RNA.

From Washington Post

Viruses depend on host cells to replicate, as do other ‘selfish’ genetic elements, such as viroids and plasmids.

From Nature

The smallest living things known, the viroids, are composed of less than 10,000 atoms.

From Literature

They started taking advantage of the cellular machinery of their DNA-based hosts, using it to churn out new viroids.

From New York Times