Epistasis
In this interaction, one gene suppress / mask the expression of other non-allelic gene.
The gene which suppress other epistasis. The gene being suppress other hypostatic
Dominance occur in allelic gene whereas epistasis occur in non-allelic gene. negative interaction.
Two type of epistasis
1. Dominant epistasis
When the dominant allele of epistasis gene suppresses the hypostasis gene.
example : hair colour in dogs
*9- W_B_ [Dogs are white in colour]
*3-W_bb [Dogs are white in colour ]
*3-wwB_[Dogs are black in colour ]
*1-wwbb [Dog are brown in colour ]
12:3:1 are the ratio of dogs skin colour
2. Recessive epistasis
When the recessive allele of epistasis allele mask the expression of hypostasis gene , (both dominant and recessive allele )
example of coat colour of mice
* 9-A_B_-The colour of is Agouti
* 4-__bb_-The colour of is Albino
* 3-aaBb-The colour of is black
recessive epistatsis ratio 9:4:3 are the ratio of the mice colour
- A in supplementary allele for B and hypoststic gene for b.
- AaBb - untill B is present b is not functional (Agouti)
-Aabb -B is absent b will suppress A (albino)