Genetic Monitoring of Outbred Stocks

Outbred stocks are subject to genetic drift as well as the possibility of genetic contamination. Any genetic monitoring scheme should aim to detect these. Also, in contrast to inbred strains, there can be no authentication stage, because there is no "correct" genotype for an outbred stock. Outbred animals with names like Wistar rats and Swiss mice from different colonies differ, and there is no international or national standard to say which is the "right" genotype. One further complication is that the outbred stock may turn out to be quite inbred if it has been maintained as a closed colony for many years. In this case, it may be quite difficult to find segregating markers suitable for monitoring genetic drift.

As with inbred strains, the preferred technical methods for monitoring outbred stocks is the use of microsatellite or other DNA-based genetic markers. However, the use of these markers is not so easy with outbred stocks, because when a locus is segregating within a colony, there may be several different alleles present. If there are small differences between alleles, classification of individual bands can become difficult. However, it should be possible to identify heterozygous animals, which have two bands.

There is no recent theoretical work on sample sizes, choice of markers, or frequency of monitoring in outbred stocks, so the suggestions given here may need to be modified according to individual experience.

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