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22-425: It is the most widely used "genetic background" for genetically modified mice for use as models of human disease. They are the most widely used and best-selling mouse strain due to the availability of congenic strains, easy breeding, and robustness. The median lifespan of C57BL/6 mice is 27–29 months and the maximum lifespan is about 36 months. The inbred strain of C57BL mice was created in 1921 by C. C. Little at

44-422: A linked segment of chromosome are defined as congenic . Similarly, organisms that are coisogenic differ in one locus only and not in the surrounding chromosome. Unlike congenic organisms, coisogenic organisms cannot be bred and only occur through spontaneous or targeted mutation at the locus. Congenic strains are generated in the laboratory by mating two inbred strains (usually rats or mice), and back-crossing

66-611: A microorganism (e.g., a virus , bacterium or fungus ). For example, a "flu strain" is a certain biological form of the influenza or "flu" virus. These flu strains are characterized by their differing isoforms of surface proteins. New viral strains can be created due to mutation or swapping of genetic components when two or more viruses infect the same cell in nature. These phenomena are known respectively as antigenic drift and antigenic shift . Microbial strains can also be differentiated by their genetic makeup using metagenomic methods to maximize resolution within species. This has become

88-456: A rice plant, all the descendants of the genetically modified rice plant are a strain with unique genetic information 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 cultivars , and if desirable plants are produced, these are further bred to stabilize

110-504: A systematic practice of reestablishing breeders from a centralized, vetted stock. The mice (as well as NOD and SJL) are known to have IgG2c allele. By far the most popular laboratory rodent, the C57BL/6 mouse accounts for 1 ⁄ 2 to 5 ⁄ 6 of all rodents shipped to research laboratories from American suppliers. Its overwhelming popularity is due largely to inertia: it has been widely used and widely studied, and therefore it

132-488: A valuable tool to analyze the microbiome . Scientists have modified strains of viruses in order to study their behavior, as in the case of the H5N1 influenza virus. While funding for such research has aroused controversy at times due to safety concerns, leading to a temporary pause, it has subsequently proceeded. In biotechnology, microbial strains have been constructed to establish metabolic pathways suitable for treating

154-400: A variety of applications. Historically, a major effort of metabolic research has been devoted to the field of biofuel production. Escherichia coli is most common species for prokaryotic strain engineering. Scientists have succeeded in establishing viable minimal genomes from which new strains can be developed. These minimal strains provide a near guarantee that experiments on genes outside

176-435: Is a stub . You can help Misplaced Pages by expanding it . Strain (biology) In biology , a strain is a genetic variant, a subtype or a culture within a biological species . Strains are often seen as inherently artificial concepts, characterized by a specific intent for genetic isolation. This is most easily observed in microbiology where strains are derived from a single cell colony and are typically quarantined by

198-437: Is considered genetically identical after 20 generations of sibling-mating. Many rodent strains have been developed for a variety of disease models, and they are also often used to test drug toxicity. The common fruit fly ( Drosophila melanogaster ) was among the first organisms used for genetic analysis , has a simple genome , and is very well understood. It has remained a popular model organism for many other reasons, like

220-400: Is unusually sensitive to pain and to cold, and analgesic medications are less effective in it. Unlike most mouse strains, it drinks alcoholic beverages voluntarily. It is more susceptible than average to morphine addiction , atherosclerosis , and age-related hearing loss . The C57BL/6 mouse was the second-ever mammalian species to have its entire genome published. The dark coat makes

242-562: Is used even more. In 1993 the first C57BL/6 gene targeted knockout mouse was published by a group at Hoffmann-La Roche in Switzerland. In 2013 C57BL/6 mice were flown into space aboard Bion-M No.1 . In 2015 C57BL/6NTac females provided by Taconic Biosciences were sent to the International Space Station on SpaceX CRS-6 . Congenic In genetics , two organisms that differ in only one locus and

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264-619: The Bussey Institute for Research in Applied Biology . The substrain "6" was the most popular of the surviving substrains. Little's supervisor William E. Castle had obtained the predecessor strain of C57BL/6, "mouse number 57", from Abbie Lathrop who was breeding inbred strains for mammary tumor research in collaboration with Leo Loeb at the time. C57BL/6 mice have a dark brown, nearly black coat. They are more sensitive to noise and odours and are more likely to bite than

286-434: The descendants 5–10 generations with one of the original strains, known as the recipient strain. Typically selection for either phenotype or genotype is performed prior to each back-cross generation. In this manner either an interesting phenotype, or a defined chromosomal region assayed by genotype, is passed from the donor strain onto an otherwise uniform recipient background. Congenic mice or rats can then be compared to

308-481: The desirable traits; the stabilized plants that can be propagated and "come true" (remain identical to the parent plant) are given a cultivar name and released into production to be used by farmers. A laboratory mouse or rat strain is a group of animals that is genetically uniform. Strains are used in laboratory experiments. Mouse strains can be inbred , mutated , or genetically modified , while rat strains are usually inbred . A given inbred rodent population

330-569: The maximum amount of background genetic information from the donor strain. This is also known as marker-assisted congenics, due to the use of genetic markers, typically microsatellite markers, but now, more commonly, single nucleotide polymorphism markers (SNPs). The process can be further aided by the superovulation of females, to produce many more eggs. Congenic strains are discussed in detail in Lee Silver's online book Mouse Genetics: Concepts and Applications : This genetics article

352-419: The minimal framework will not be effected by non-essential pathways. Optimized strains of E. coli are typically used for this application. E. coli are also often used as a chassis for the expression of simple proteins. These strains, such as BL21, are genetically modified to minimize protease activity, hence enabling potential for high efficiency industrial scale protein production . Strains of yeasts are

374-551: The more docile laboratory strains such as BALB/c . They are good breeders. Group-housed B6 male mice display barbering behavior, in which the dominant mouse in a cage selectively removes hair from its subordinate cage mates. Mice that have been barbered have large bald patches on their bodies, commonly around the head, snout, and shoulders, although barbering may appear anywhere on the body. Both hair and whiskers may be removed. C57BL/6 has many unusual characteristics that make it useful for some work and inappropriate for others: It

396-596: The most common subjects of eukaryotic genetic modification, especially with respect to industrial fermentation . 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 either descended from a modified plant (produced by conventional breeding or by biotechnological means), or which result from genetic mutation. As an example, some rice strains are made by inserting new genetic material into

418-447: The mouse strain convenient for creating transgenic mice: it is crossed with a light-furred 129 mouse, and the desirable crosses can be easily identified by their mixed coat colors. There now exist colonies of mice derived from the original C57BL/6 colony that have been bred in isolation from one another for many hundreds of generations. Owing to genetic drift these colonies differ widely from one another (and, it goes without saying, from

440-416: The original mice isolated at the Bussey Institute ). Responsible scientists, including those at accredited repositories, are careful to point out this fact and take pains to distinguish sublines such as C57BL/6J (the established subline at The Jackson Laboratory ) from C57BL/6N, etc. But even within these sublines, the potential for drift exists in colonies maintained by individual laboratories who do not have

462-422: The physical constraints of a Petri dish . Strains are also commonly referred to within virology , botany , and with rodents used in experimental studies . It has been said that "there is no universally accepted definition for the terms 'strain', ' variant ', and 'isolate' in the virology community, and most virologists simply copy the usage of terms from others". A strain is a genetic variant or subtype of

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484-403: The pure recipient strain to determine whether they are phenotypically different if selection was for a genotypic region, or to identify the critical genetic locus, if selection was for a phenotype. Speed congenics can be produced in as little as five back-cross generations, through the selection at each generation of offspring that not only retain the desired chromosomal fragment, but also 'lose'

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