John's parents are "Both heterozygous for the alkaptonuria gene."
Alkaptonuria (AKU) is a prototypic inherent error in the digestion of phenylalanine and tyrosine, portrayed by the failure to use homogentisic acid. AKU is caused by homozygous or compound heterozygous transformations and was likewise demonstrated that AKU is caused additionally by the obviously fractional loss‐of‐function changes, nonetheless, the heterozygous bearers of AKU are healthy.
