What is the difference between multiple gene action and multiple allelism? Give examples of both

The multiple or pleiotropic effect of a gene is when one gene can influence the development of different traits. In Drosophila, the recessive allele of one of the genes determines the absence of eye pigment (biloba), the light color of the body, changes the structure of the genitals, reduces the fecundity and longevity. In potatoes, the dominant allele of a certain gene determines the pink color of tubers and the red-violet corolla (in plants, homozygous for the corresponding recessive gene, tubers and corollas of flowers are bluish or white).
Multiple allelism is the existence of more than two variants of one gene. The reason is multiple mutations of the same gene. An example is the inheritance of blood groups according to the ABO system. Variants of eye color in a fruit fly.

Remember: The process of learning a person lasts a lifetime. The value of the same knowledge for different people may be different, it is determined by their individual characteristics and needs. Therefore, knowledge is always needed at any age and position.