Ambidirectional dominance occurs in a situation where multiple

gene In biology, the word gene (from , ; "...Wilhelm Johannsen coined the word gene to describe the Mendelian units of heredity..." meaning ''generation'' or ''birth'' or ''gender'') can have several different meanings. The Mendelian gene is a b ...

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 (biology), morphology or physical form and structure, its Developmental biology, developmental proc ...

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 a ...

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 The paradise fish, paradise-fish, paradisefish, or paradise gourami (''Macropodus opercularis'') is a species of gourami found in most types of fresh water in East Asia, ranging from the Korean Peninsula to northern Vietnam. This species can ...

References

Genetics Selection {{genetics-stub