Much of the early progress in biochemical genetics was descriptive. Keen clinical observations enabled the characterization of many disorders. Often, these descriptions relied on clinical observations of easily recognizable changes, such as urine color (dark urine in alkaptonuria) or odor (the smell of maple syrup in maple syrup urine disease or sweaty feet in isovaleric acidemia). Simple chemical tests, such as the use of ferric chloride, enabled the description of still more disorders.
Forty years ago, the discovery of a single amino acid substitution in the hemoglobin molecule and the resulting disease, sickle cell anemia, marked the beginning of a new era in biochemical genetics. For the first time, it was shown that protein structure affected function. The description by Watson and Crick1 of the molecular basis of heredity permitted the understanding of the genetic code and allowed for the present understanding of inherited diseases. Disorders could be understood
Levy P, Shapira E. State of the Art of Biochemical Genetics. Am J Dis Child. 1993;147(11):1153-1158. doi:10.1001/archpedi.1993.02160350027004