Inbred strains of mice are defined as strains that have been maintained by successive brother to sister matings over more than 20 generations (Green, 1975). Repetitive inbreeding removes genetic heterogeneity, so that mice of an inbred strain are considered to be genetically identical to each other.

What happens if mice inbreed?

Mice have been inbred to reduce genetic variance for over a 100 years, and each generation of inbreeding is expected to lead to a decrease in heterozygosity (Wright 1921; Silver 1995).

Is inbreeding bad for mice?

Mating between close relatives is avoided in many animals because it can lead faulty, otherwise hidden (or recessive) traits that are shared between them to surface in their offspring, a phenomenon known as inbreeding depression, the researchers explained. ...