Why is it important to understand the overall relationship between genes, proteins, and chemical reactions in cells?

A) Many changes in the morphology or behavior of organisms can be linked to variations in the proteins and genes that build them.
B) Genetic effects on the biology of organisms account for as much as 10% of the variation we see from species to species.
C) Although most evolutionary change is extracellular, it is sometimes influenced by genetic systems.
D) Only by controlling these relationships can we treat most disease symptoms.