How to find the number of pair of alleles involved in polygenic inheritance using the number of phenotypical forms of the trait they condition?
Considering the "p" number of the phenotypical forms and "a" the number of involved alleles of the polygenic inheritance. The formula is p = 2a + 1 is then applied.
(Many times it isn't possible to determine precisely the number of phenotypical forms, p, due to the multigenic feature of the inheritance, ever since often the observed variation of phenotypes seems to be on a continuum or the trait suffers environmental influence.)