Table 2.

Main points of mixed model updated from polygenic model

Polygenic model	Mixed model a
All variable genes have two possible alleles	Many variable genes have more than two alleles in fact
Each contributing gene has small and relatively equal effects	Effect size of each contributing gene is not entirely equal; there are both major and minor genes 57
The allele effects of each gene are only additive	Besides additive, the allele effects of certain genes are also non-additive on some occasions 58
There is no dominance on each locus	There are (over-, co-, partial or incomplete) dominance loci 59,60
There is no epistasis or interaction among different loci contributing to the target trait	There often is epistasis or complex interaction among different loci contributing to the target trait 25,61,62
The genes are segregating independently	There are linkages between loci 63-65
Target trait depends solely on genetics, and environmental influences can be ignored	The merit of target trait depends on genetic and environmental factors and their interactions 66,67
a So far, there has been a lack of a one-time thorough depiction of mixed model. The updates of the mixed model from polygenic one have been gradually solved by separate and fragmentary investigations.