Coisogenic strains are one type of

inbred strain Inbred strains (also called inbred lines, or rarely for animals linear animals) are individuals of a particular species which are nearly identical to each other in genotype due to long inbreeding. A strain is generally defined to be inbred once it ...

that differs by a mutation at a single

locus Locus (plural loci) is Latin for "place". It may refer to: Mathematics and science * Locus (mathematics), the set of points satisfying a particular condition, often forming a curve * Root locus analysis, a diagram visualizing the position of r ...

and all of the other loci are identical. There are numerous ways to create an inbred strain and each of these strains are unique. Genetically engineered mice can be considered a coisogenic strain if the only difference between the engineered mouse and a wild-type mouse is a specific locus. Coisogenic strains can be used to investigate the function of a certain genetic locus. Coisogenic strains can be induced chemically or through radiation however, other types of alterations within the genome may also occur. Coisogenic strains may also occur through a spontaneous mutation that occurs in an inbred strain. To create a coisogenic strain through breeding, a mouse with the specific mutation on a locus is mated to an inbred strain (e.g.,

C57BL/6 C57BL/6, often referred to as "C57 black 6", "B6", "C57" or "black 6", is a common inbred strain of laboratory mouse. It is the most widely used "genetic background" for genetically modified mice for use as models of human disease. They are the ...

J) mouse. The offspring of the mutated mouse with the inbred strain has a 50% chance of carrying the mutation. From this, the offspring with the mutation can be mated to a heterozygous carrier which then creates offspring with 75% of the genetic background. This

backcrossing Backcrossing is a crossing of a hybrid with one of its parents or an individual genetically similar to its parent, to achieve offspring with a genetic identity closer to that of the parent. It is used in horticulture, animal breeding, and produc ...

is then continued until more than 99% is genetic background and the mutated locus is inherited. However, if the specific mutation cannot be passed on, heterozygous animals should be used to breed with the original inbred strain. Full-sib mating are used to maintain coisogenic strains if the specific gene locus is homozygous. However, a regular backcrossing of these coisogenic strains with their standard parental strain is preferred in order to avoid subline divergence.

References

{{Reflist Model organisms Laboratory mice Laboratory rats Animal breeding