Polygene refers to the gene which exerts a slight effect on a phenotype along with other genes.
Effect of a single gene is too small, so it is very difficult to detect.
Multiple genes also produce an equal effect.
Each allele has a cumulative or additive effect.
The colour of the eye is determined by the polygenes.
At least 9 colours of eye colour are recognised in humans. There are two major eye colour genes and 14 more genes which determine the expression of the phenotype.