How small can Sanger DNA sequencing go?
Since the development of DNA sequencing, scientists have been trying to do it less expensively
and with less sample. There are various ways to sequence DNA, but the Sanger method
generates long and accurate sequence reads, which is important for comparative analysis
of variations such as insertions and deletions in mammalian genomes.
Richard A. Mathies and colleagues at the University
of California campuses in Berkeley and in San Francisco have created a microdevice
that can perform Sanger sequencing using only 1 fmol of DNA template. The device
is made of a hybrid glass PDMS assembly, a critical change from the monolithic substrate
used before. It incorporates miniaturized temperature sensing, nanoliter scale Sanger
extension reactions, microvalves/pumps, DNA affinity-capture and high-performance
In the May 9 issue of PNAS,
the researchers report that the device can sequence up to 556 continuous bases with
99 percent accuracy, which is adequate for de novo sequencing (determining DNA sequence
without any prior knowledge of that sequence) of human and other genomes. They used
this information to predict an ultimate limit of Sanger sequencing miniaturization.
They believe that, by incorporating other advancing technologies such as more efficient
injection techniques and scanners with improved sensitivity, the 1-fmol sample required
could be reduced, conservatively, to 100 amol and possibly to as little as ~10
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