GENETICS × TECHNOLOGY

Reading DNA

1977 CE

Phanerozoic · Cenozoic · Quaternary · Holocene · Meghalayan

A chemistry that stops a growing DNA strand at each of the four bases, then sorts the fragments by length, turns a molecule into a text you can read off letter by letter. Two methods appeared in the same year, from Cambridge and from Harvard; the chain-termination one won on practicality and carried genetics for thirty years. The first genome read this way belonged to a virus, and ran to 5,386 letters.

Why it matters

Every genome on this page was read with a descendant of this method: the Neanderthal, the plague bacterium, the ancient wolves, our own. The step from 5,386 letters to three billion took twenty-four years, and the step from three billion to a genome recovered from a finger bone took ten more.

Dating & uncertainty

Two methods appeared the same year, from Cambridge and from Harvard. The chain-termination method won on practicality and carried genetics for thirty years.

Sources

1. Sanger, Nicklen & Coulson (1977), PNAS · DNA sequencing with chain-terminating inhibitors
2. Maxam & Gilbert (1977), PNAS · A new method for sequencing DNA
3. Heather & Chain (2016), Genomics · The sequence of sequencers: the history of sequencing DNA

Earth history as one day

23:59:59.9991933 µs before midnight

if Earth’s 4.54 billion years were compressed into a single day