<Li> Polygenic characters show a continuous rather than discontinuous distribution . </Li> <Li> Balanced systems of polygenic inheritance in a population contain a great deal of potential genetic variability in the heterozygous condition and released by small increments through genetic recombination between linked polygenes . </Li> <P> Polygenic inheritance occurs when one characteristic is controlled by two or more genes . Often the genes are large in quantity but small in effect . Examples of human polygenic inheritance are height, skin color, eye color and weight . Polygenes exist in other organisms, as well . Drosophila, for instance, display polygeny with traits such as wing morphology, bristle count (20170808 dead link) and many others . </P> <P> The frequency of the phenotypes of these traits generally follows a normal continuous variation distribution pattern . This results from the many possible allelic combinations . When the values are plotted, a bell - shaped curve is obtained . The mode of the distribution represents the optimal, or fittest, phenotype . The more genes are involved, the smoother the estimated curve . However, in this model all genes must code for alleles with additive effects . This assumption is often unrealistic as many genes display epistasis effects which can have unpredictable effects on the distribution of outcomes, especially when looking at the distribution on a fine scale . </P>

In human beings multiple genes are involved in the inheritance of