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. And so instead of converting the phenolalanine into tyrosine, what our body will do is it will convert the phenylalanine into toxic substances. And as a result, over time, the accumulation and the build up of the toxic substances will damage the central nervous system and that will lead to many different types of mental abnormalities and mental disabilities. So this is what we mean by pheno keto Neuria.