DISEASE or  CONDITION	PHENOTYPE	PROTEIN	TYPE	PROTEIN  FUNCTION	BIOCHEMICAL RESULT OF REDUCED FUNCTION OF PROTEIN VARIANT
Alkaptonuria	Dark nose and ears.  Darkened joints.  Black urine.  Arthritis.	Homogentisic Acid Oxidase	Enzyme	oxidizes and opens phenyl ring of HA to 8-C maleyl acetoacetic acid	Homogentisic Acid (HA) is not oxidized, and accumulates to high levels.  Since it is a phenolic compound, it oxidizes easily to dark colored products.  These are deposited in cartilage and other soft tissues of the body.
Phenylketonuria	Light complexion, fair hair and blue eyes.  MENTAL RETARDATION.	Tyrosine Hydroxylase	Enzyme	hydroxylates phenylalanine to tyrosine	Phenylalanine is not hydroxylated, and instead accumulates.  When high concentrations are reached, phenylalanine is metabolized in an alternate pathway.  These metabolites are toxic to developing cells of the CNS and brain.
Albinism	Lack of pigmentation results in white hair and skin, and appearance of pink eyes.	Tyrosine hydroxylase  Tyrosinase	Enzyme	hydroxylates tyrosine to DOPA  converts DOPA to melanin precursors	No dihydroxyphenylalanine (DOPA) produced.  Without DOPA as a precursor for downstream reactions, no melanin can be produced.