The Discovery of DNA

Nucleic acids were identified well before their genetic role was understood. In 1869, the Swiss biochemist Friedrich Miescher isolated a phosphorus-rich, acidic substance from the nuclei of white blood cells recovered from pus-soaked surgical bandages: a weak alkaline solution lysed the cells and precipitated their nuclei, from which he extracted this new chemical. Because it came from the nucleus, he called it 'nuclein'; its high phosphorus content and acidic behaviour later led to the name 'nucleic acid'. By the early twentieth century, biochemists had realised that Miescher's nuclein was actually a mixture of proteins bound to two distinct kinds of nucleic acid -- deoxyribonucleic acid (DNA) and ribonucleic acid (RNA). This discovery set the stage for the search, spanning the following decades, to determine which chromosomal component -- protein or DNA -- actually carried hereditary information from one generation to the next.