One complete copy of the human genome is written in chemical letters called base pairs. How many of them does it contain?
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Answer
About 3.1 billion base pairs
The first truly gapless human genome sequence was only published in 2022, almost two decades after the Human Genome Project was declared finished.
How to estimate it
Stretched out, the DNA in one human cell would measure about 2 metres. Neighbouring base pairs sit 0.34 nanometres apart along the double helix. 2 m / 0.34 nm gives about 6 billion base pairs. A cell holds two copies of the genome, one from each parent, so a single copy has half of that: about 3 billion. The sequenced value is about 3.1 billion base pairs.
Source: US National Human Genome Research Institute; T2T Consortium 2022
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