GENETICS × TECHNOLOGY

Copying DNA at Will

1983 to 1985 CE

Phanerozoic · Cenozoic · Quaternary · Holocene · Meghalayan

Heat separates the two strands of a DNA molecule; cooling lets short primers settle on the stretch you want; an enzyme copies it; then the heat returns and the cycle begins again. Each round doubles what you have, so one molecule becomes a billion in an afternoon. It only became routine once the copying enzyme was borrowed from a bacterium that lives in hot springs. That enzyme survives the heating step instead of having to be replaced every cycle.

Why it matters

Ancient bones, a crime scene, a virus on a nasal swab: each holds DNA in quantities far too small to read. This is the step that makes them readable, and several of the discoveries further along this timeline happened only because of it.

Dating & uncertainty

The two dates are the idea, in 1983, and the first published use, in 1985. What made the method ordinary came two years later still.

Sources

1. Saiki et al. (1985), Science · Enzymatic amplification of beta-globin genomic sequences and restriction site analysis for diagnosis of sickle cell anemia
2. Mullis (1990), Scientific American · The unusual origin of the polymerase chain reaction
3. Heather & Chain (2016), Genomics · The sequence of sequencers: the history of sequencing DNA

Earth history as one day

23:59:59.9992818 µs before midnight

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