Illustration of Inborn errors of metabolism

1909 Inborn errors of metabolism

The book of science

Tom Sharp

Archibald Garrod genetics Illustration of Inborn errors of metabolism

Inborn errors of metabolism

Alkaptonuria darkens the urine due to an incomplete digestion of tyrosine from proteins in the diet. Archibald Garrod discovered if you don’t get a working gene for a particular enzyme from at least one parent then you inherit alkaptonuria.


Enzymes catalyze chemical transformations that let us digest our food and grow our bodies. From missing these enzymes springs disorders that are inherited in families, such as albinism, caused by a defect in an enzyme needed to produce melanin, and maple syrup urine disease, caused by defects in an enzyme complex that makes an infant’s urine smell like maple syrup, another case in which our bodies seem more like alien creatures.


Born without an appendix he knew he would never get appendicitis. But could he pass on these benefits to a future generation? No; chances were that his future wife would not have the same mutation, or, worse, that he would be scorned because he is subtly a little different.

Many people whom I have known might have suspected me, but I will neither confirm nor deny that I am a mutant. If I weren’t, at least I might have a recessive gene or two that could express themselves against the norm in another context.

See also in The book of science:

Readings in wikipedia: