The longtime goal of a $1,000 genome is still just out of reach, a Harvard University physicist is promising an even cheaper price–the ability to sequence a human genome for just $30. David Weitz and his team are adapting microfluidics technology that uses tiny droplets, a strategy developed in his lab, to DNA sequencing. While the researchers have not yet sequenced DNA, they have successfully demonstrated parts of the process and formed a startup, GnuBio, to commercialize the technology.
* Weitz’s team had previously developed a way to create picoliter droplets of water, which act as tiny test tubes. The droplets can be precisely moved around on a microfluidics chip, injected with chemicals and sorted based on color.
* Smaller drops means smaller volumes of the chemicals used in the sequencing reaction. These reagents comprise the major cost of sequencing, and most estimates of the cost to sequence a human genome with a particular technology are calculated using the cost of the chemicals. Based solely on reagents, Weitz estimates that they will be able to sequence a human genome 30 times for $30.
In Weitz’s approach, droplets are injected with short strands of DNA of a known sequence, and these strands are labeled with an optical bar code. Pieces of the sample with an unknown sequence are also injected into the droplets–if the sample has a stretch of sequence complementary to the known strand, the two pieces will bind, triggering a change in color. Repeat this 1,000 times with 1,000 different known strands and you can generate the sequence of 1,000 letters of DNA, says Weitz.
Both the optical bar code and the color change are detected using a microscope and camera with automated detection software. Weitz says they can produce and process a million drops per second.