The encyclopedia · R&D & Science · Technical decision · 1975–1977
Sanger's chain-terminator method made reading DNA fast and accurate
Frederick Sanger stopped DNA copies at each base with dideoxy nucleotides, so fragment length revealed the sequence — faster and more accurate than before.
MRC Laboratory of Molecular Biology
The solution
In 1975 Sanger and Coulson had published the 'plus and minus' method for reading DNA, but it was slow and error-prone. In their 1977 paper in PNAS they described an improvement: 2',3'-dideoxy and arabinonucleoside analogues of the normal nucleotides, which act as specific chain-terminating inhibitors of DNA polymerase.
The insight turns synthesis into a measurement: in four parallel reactions, each containing one dideoxy terminator, every newly made strand stops at a specific base. Separated by length, the collection of fragments spells out the whole sequence. The authors applied it to the genome of bacteriophage phiX174 and reported it 'more rapid and more accurate' than the earlier methods.
Chain-terminator sequencing became the dominant sequencing technology for two decades — the basis of the automated sequencers that read the human genome — and Sanger received his second Nobel Prize in Chemistry in 1980.
Why it worked
- Chain terminators create a complete set of stopping points
- Fragment length directly encodes base position
- One simple chemistry replaced laborious degradation analysis
- Easily automated, which enabled the genome era
What can be applied
To measure where things are along a chain, create a ruler by stopping the process at every position — the fragment lengths do the measuring for you.
Aftermath
Applied Biosystems automated the method, and chain-terminator (Sanger) sequencing powered the Human Genome Project, remaining the gold standard for accuracy until next-generation sequencing took over in the late 2000s. Sanger won the 1980 Nobel Prize in Chemistry for the work.
Sources
- DNA sequencing with chain-terminating inhibitors
- Frederick Sanger — Nobel Lecture: Determination of Nucleotide Sequences in DNA
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