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Strain (biology)

Strain (biology)

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In biology
Biology
Biology is a natural science concerned with the study of life and living organisms, including their structure, function, growth, origin, evolution, distribution, and taxonomy. Biology is a vast subject containing many subdivisions, topics, and disciplines...

, a strain is a low-level taxonomic rank
Taxonomic rank
In biological classification, rank is the level in a taxonomic hierarchy. Examples of taxonomic ranks are species, genus, family, and class. Each rank subsumes under it a number of less general categories...

 used in three related ways.

Microbiology and virology


A strain is a genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 variant or subtype of a micro-organism (e.g. virus
Virus
A virus is a small infectious agent that can replicate only inside the living cells of organisms. Viruses infect all types of organisms, from animals and plants to bacteria and archaea...

 or bacterium or fungus
Fungus
A fungus is a member of a large group of eukaryotic organisms that includes microorganisms such as yeasts and molds , as well as the more familiar mushrooms. These organisms are classified as a kingdom, Fungi, which is separate from plants, animals, and bacteria...

). For example, a "flu strain" is a certain biological form of the influenza
Influenza
Influenza, commonly referred to as the flu, is an infectious disease caused by RNA viruses of the family Orthomyxoviridae , that affects birds and mammals...

 or "flu" virus. Compare clade
Clade
A clade is a group consisting of a species and all its descendants. In the terms of biological systematics, a clade is a single "branch" on the "tree of life". The idea that such a "natural group" of organisms should be grouped together and given a taxonomic name is central to biological...

.

Plants


The term has no official ranking status in botany; the term refers to the collective descendants produced from a common ancestor that share a uniform morphological or physiological character. A strain is a designated group of offspring that are descended from a modified plant, produced by conventional breeding, by biotechnological means, or result from genetic mutation.

As an example, some rice
Rice
Rice is the seed of the monocot plants Oryza sativa or Oryza glaberrima . As a cereal grain, it is the most important staple food for a large part of the world's human population, especially in East Asia, Southeast Asia, South Asia, the Middle East, and the West Indies...

 strains are made by inserting new genetic
Genetics
Genetics , a discipline of biology, is the science of genes, heredity, and variation in living organisms....

 material into a rice plant, all the descendant
Lineal descendant
A lineal descendant, in legal usage, refers to a blood relative in the direct line of descent. The children, grandchildren, great-grandchildren, etc...

s of the genetically modified rice plant are a strain with a unique genetic code
Genetic code
The genetic code is the set of rules by which information encoded in genetic material is translated into proteins by living cells....

 that is passed on to later generations; the strain designation, which is normally a number or a formal name, covers all the plants that descend from the originally modified plant. The rice plants in the strain can be bred to other rice strains or cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...

s, and if desirable plants are produced, these are further bred to stabilize the desirable traits; the stabilized plants that can be propagated and "come true" (remain identical to the parent plant) are given a cultivar
Cultivar
A cultivar'Cultivar has two meanings as explained under Formal definition. When used in reference to a taxon, the word does not apply to an individual plant but to all those plants sharing the unique characteristics that define the cultivar. is a plant or group of plants selected for desirable...

 name and released into production to be used by farmers.

Rodents


A mouse
Mouse
A mouse is a small mammal belonging to the order of rodents. The best known mouse species is the common house mouse . It is also a popular pet. In some places, certain kinds of field mice are also common. This rodent is eaten by large birds such as hawks and eagles...

 or a rat
Rat
Rats are various medium-sized, long-tailed rodents of the superfamily Muroidea. "True rats" are members of the genus Rattus, the most important of which to humans are the black rat, Rattus rattus, and the brown rat, Rattus norvegicus...

 strain is a group of animals that is genetically uniform. Strains are used in laboratory experiments. Mouse strains can be inbred, mutated or genetically engineered, while rat strains are usually inbred.

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