Final answer:
Proteins serve as the bridge between genotype and phenotype. Genes code for proteins, and the production of different proteins influences the observable characteristics of an individual, or the phenotype.
Step-by-step explanation:
Proteins serve as the bridge between genotype and phenotype. The genotype is the collection of genes that an individual possesses, while the phenotype is the observable characteristics resulting from those genes. Genes code for proteins, and specific proteins being produced by the cell at a given time influence the phenotype. The production of different proteins leads to different phenotypes, as proteins play important roles in nearly every cell function and influence the traits displayed by organisms.