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We鈥檝e yet to finish sequencing the entire human genome 鈥� but we have just filled in a few of the remaining gaps thanks to a tiny, cheap DNA sequencer.

Some parts of the human genome consist of short sequences repeated over and over again. Conventional DNA sequencing methods can only read a few hundred DNA letters at a time, so it has not been possible to fully sequence the most repetitive stretches of DNA 鈥� little pieces can be sequenced but there is no way to join these pieces up in the right order.

But the MinION sequencer made by Oxford Nanopore can now read well over a million DNA letters at a time, says of the University of Nottingham in the UK, whose team is the first to use it to sequence the entire genome of one individual. It is not as accurate as other sequencing methods, but is improving fast.

鈥淭his shows just how far the technology has come,鈥� says Loose. 鈥淚t鈥檚 quite cool that you can sequence the human genome on a sequencer you can throw in your back pocket.鈥�

While the actual sequencer is little bigger than a USB stick, other equipment is needed to prepare human DNA for sequencing. Analysing the raw data also requires a computer with a powerful graphics processor. You could just about get it all in a backpack, says Loose, but it would be a very heavy backpack.

Portability is not a big deal for human genome sequencing, says Loose 鈥� it has long been possible to send samples off for sequencing elsewhere, for instance. The appeal of the MinION is that it is cheap, easy to use and, thanks to the long reads, can reveal genome rearrangements that other methods miss.

However, portability can be a big plus for biologists working in the field who need quick answers, such as those investigating Ebola outbreaks, say Loose. Preparing viral or bacterial DNA for sequencing requires much less equipment than for the human genome.

The team鈥檚 results will be integrated into the Human Genome Project鈥檚 鈥渞eference鈥� genome, says Kerstin Howe of the Wellcome Trust Sanger Institute in the UK, who helps oversee it. Accurately sequencing the human genome will require a variety of approaches, she says, as there are problems with all methods. 鈥淭here鈥檚 no single answer.鈥�

The highly repetitive parts of human DNA are not thought to be important in determining our traits or our risk of getting certain diseases. But sequencing them could still reveal useful information about evolution, says Howe.