DNA is now a household word, but its existence was unknown until 1869. During that year, Johann Friedreich Miescher II first isolated DNA from cells. Born in Basel, Switzerland in 1844, he was the son and nephew of distinguished anatomists at the University of Basel. Miescher himself studied medicine at the University, but decided to study chemistry instead because he was concerned that his partial deafness, caused by an earlier bout with typhus, would impair his ability as a physician.

Miescher became a student of Felix Hoppe-Seyler, whose laboratory was located in the castle of Tubingen, Germany. In 1869, Miescher collected the dressings of wounded soldiers and scraped the pus off the dressings. From the white blood cells in the pus he isolated the nuclei from the cytoplasm; and from the nuclei, he extracted a substance that contained phosphorus in addition to the carbon, hydrogen, oxygen, and nitrogen typically found in...