The reaction rate is the limits of the modification variability of the trait. Some signs, for example, leaf length, plant height, animal body weight, cattle milk production, hen egg production, have a wide reaction rate. Others, for example, the size of the flowers and their shape, the color of the seeds, flowers and fruits, the color of the animals, the fat content of milk, are the more narrow reaction norm.
The reaction rate is determined by the genotype and is inherited. For example, the more time a person spends in direct sunlight, the more melanin is synthesized in open areas of the skin and, accordingly, its color is darker. As you know, the intensity of tanning is not inherited, but is determined by the specific living conditions of a person. In addition, even in a Caucasian person who is constantly in direct sunlight, the skin cannot synthesize the amount of melanin that is characteristic, for example, of representatives of the black race. This example indicates that the range of variation of the trait (reaction rate) is predetermined by the genotype and not the trait itself is inherited, but the body’s ability to form a specific phenotype under the influence of environmental conditions.