Ambidirectional dominance occurs in a situation where multiple

gene In biology, the word gene has two meanings. The Mendelian gene is a basic unit of heredity. The molecular gene is a sequence of nucleotides in DNA that is transcribed to produce a functional RNA. There are two types of molecular genes: protei ...

s influence a

phenotype In genetics, the phenotype () is the set of observable characteristics or traits of an organism. The term covers the organism's morphology (physical form and structure), its developmental processes, its biochemical and physiological propert ...

and dominance is in different directions depending on the gene. For example, for

A increased height is dominant, while for

B decreased height is dominant. The opposite situation, where all genes show dominance in the same direction, is called directional dominance. In the same example, for both genes A and B increased height is dominant. According to Broadhurst, ambidirectional dominance is the result of

stabilising selection Stabilizing selection (not to be confused with negative or purifying selection) is a type of natural selection in which the population mean stabilizes on a particular non-extreme trait value. This is thought to be the most common mechanism of ...

in the evolutionary past. Ambidirectional dominance has been found for exploratory behaviours in

mice A mouse (: mice) is a small rodent. Characteristically, mice are known to have a pointed snout, small rounded ears, a body-length scaly tail, and a high breeding rate. The best known mouse species is the common house mouse (''Mus musculus' ...

and paradise fish.

References

Genetics Selection {{genetics-stub