Palygenic inheritance example
Answers
Skin pigmentation: in humans
Kernel colour of the wheat : in plants
The pigment melanin is responsible for dark coloration in the skin and there are at least three genes, which control for human skin color. Using a hypothetical example where the production of melanin is controlled by contributing alleles (denoted here as A, B and C), resulting in dark skin color, and therefore light skin color is produced by non contributing alleles (denoted here as a, b and c), it is possible to see how the spectrum of different skin colors can result in the offspring.
It is important to remember here that in polygenic inheritance, alleles do not display dominance over others, rather, each contributing allele gives an additive effect rather than a masking effect, and so the way that the alleles interact is different to those in Mendelian genetics. The additive effect means that each contributing allele produces one unit of color.
In an example using two parents, heterozygous for each of the melanin-producing genes (AaBbCc x AaBbCc), it is possible to see how the additive effects and combinations of alleles results in all the possible genotypes.