Phenotype is depending on the underlaying genotype

Students generally have a hard time understanding a phenotypes dependency on the underlaying genotype. A dominant trait can be manifested by only one copy of a gene (heterozygote) which will yield a functional protein. This is illustrated by using a water hose as an example, one blueprint is sufficient to make a functional water hose. Without blueprints, however, it is not possible to make a functional water hose.