autosomal recessive fashion<unk>  is an autosomal recessive metabolic genetic disorder. As an autosomal recessive disorder, two<unk>  alleles are required for an individual to experience symptoms of the disease. For a child to inherit<unk> , both the mother and father must have and pass on the defective gene. If both parents are carriers for<unk> , there is a 25% chance any child they have will be born with the disorder, a 50% chance the child will be a carrier and a 25% chance the child will neither develop nor be a carrier for the disease.<unk>  is characterized by homozygous or compound heterozygous mutations in the gene for the hepatic enzyme phenylalanine hydroxylase (PAH), rendering it nonfunctional. This enzyme is necessary to metabolize the amino acid phenylalanine (Phe) to the amino acid tyrosine (Tyr). When PAH activity is reduced, phenylalanine accumulates and is converted into phenylpyruvate (also known as phenylketone), which can be detected in the urine. Carriers of a single<unk>  allele do not exhibit symptoms of the disease but appear to be protected to some extent against the fungal toxin ochratoxin A. This accounts for the persistence of the allele in certain populations in that it confers a selective advantage—in other words, being a heterozygote is advantageous. The PAH gene is located on chromosome 12 in the bands 12q22-q24.2. As of 2000, around 400 disease-causing mutations had been found in the PAH gene. This is an example of allelic genetic heterogeneity.
Phenylketonuria
Hawkinsinuria
Homocystinuria
Alkaptonuria
3-Methylglutaconic aciduria
2-Hydroxyglutaric aciduria
Alpha-aminoadipic and alpha-ketoadipic aciduria
Aspartylglucosaminuria