1 In outbred populations, selection acts on new mutations mainly through their heterozygous effects.

2 The breeding system adopted depends on the number of animals required and whether they are of an inbred or outbred strain.

3 Selfing heterozygotes halves the heterozygosity , and thus outbreeding maintains heterozygosity and produces a more adaptable population.

4 If inbreeding is bad, then the opposite – outbreeding – should be good.

5 Selfing heterozygotes halves the heterozygosity, and thus outbreeding maintains heterozygosity and produces a more adaptable population. Compare homozygous.

6 However, it is worth emphasizing here that at least four costs have been proposed for inbreeding, and at least seven for outbreeding.