Two organisms are said to be isogenic if they are genetically identical.
Monozygous twins in humans, cattle and some other mammals are isogenic. However, their use in research is limited by their rarity.
Inbred strains of mice and rats are isogenic. They are like immortal clones of genetically identical individuals which can be reproduced at will. They are the nearest equivalent of the analytical grade chemical that is available with a living mammal and are the animals of choice for most research involving these species.
A black-and-tan (at) fancy mouse. Note that they are bred to hold their tail at 45o
Isogenic strains of rodents have many advantages as research animals.
- Genetic similarity leads to phenotypic uniformity so that fewer animals are needed in an experiment to achieve a given level of statistical power.
- Each strain has unique characteristics, some of which may be of value in a particular research project. Some strains can be used as models of specific human diseases such as diabetes or cancer.
- Information on strain characteristics accumulates as research workers throughout the world use genetically identical animals.
- The strains stay constant for many generations: the only way that they can change, barring contamination, is as a result of the fixation of new mutations which are relatively rare. However research workers need to be aware of differences arising from mutations in sub-strains which have been separated for several years.
- Genotyping of a single animal is sufficient to genotype the whole strain.
- An experiment using small numbers of animals of several strains can be done without increasing the total number of animals. It will show the extent to which a particular response is under genetic control.
Suggested way to use this site.
Look at the quotes from geneticists, which go back over 70 years.
If you are interested in toxicity testing, click that button or here to see why the use of isogenic strains would increase the power of toxicological testing.
Donít forget the ethics of using laboratory animals. Click that button.
The Isogenic strains button has 12 sub-pages which tell you about the properties, nomenclature, breeding, quality control, history and strategy in the use of isogenic strains and their derivatives such as congenic strains.
In many studies it makes sense to use more than one strain. This can often be done without using any more animals than if a single strain were to be used. The Multi-strain experiments button tells you why.
You may want to know more about the properties of outbred stocks, and why they may not be suitable for much modern biomedical research. Click the Outbred stocks button.
Then there are some FAQs, and something about the author of this site, with contact details.