Many traits of living organisms are controlled by a single pair of allelic genes. Various types of interactions are observed between allelic genes. In some cases, the result of this interaction may be the appearance of a qualitatively new trait that was not determined individually by any of the genes (for example, in a person, the coding of the IA and IB genes leads to the formation of blood group IV).
At the same time, a huge number of characters are known in living organisms that are controlled not by one, but by two or more pairs of genes. The interaction of non-allelic genes determines, for example, growth, body type and skin color in humans, coat color and plumage in many mammals and birds, shape, size, color of fruits and seeds of plants, etc. The opposite phenomenon is often observed when one pair of allelic genes affects several signs of the body at once. In addition, the action of some genes can be altered by the proximity of other genes or environmental conditions.
Thus, genes are closely related and interact with each other. Therefore, the genotype of any organism cannot be considered as a simple sum of individual genes. Genotype is a complex holistic system of interacting genes.
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.