Well, under normal conditions, in individuals who are homozygous dominant or are heterozygous, they have this gene that codes for a special protein that breaks down the phenolamine amino acid into another amino acid known as tyrosine. So let's suppose that inside the somatic cell of my body, I have this particular genotype. So what that means is because I have at least one of these normal genes, that gene will be able to code for a special protein that breaks down that basically converts phenylalamine into tyrosine. So every time I ingest the phenylalamine, my body, my cells will have this enzyme to convert it into tyrosine. Now, in homozygous recessive individuals, however, they don't have that proper gene that is needed to form that enzyme. And as a result, that enzyme will not be able to convert the phenoalamine into tyrosine.