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Sequencing Life


Fall sick in the future and you could get medicine tailored to your DNA. 
 
Professor Yu Hao and his team have developed a more accurate and low-cost way to sequence a person’s DNA at high resolution, which will enable more personalised medicine.  
 
Their technique relies on optical and chemical methods to identify DNA’s different neuclotide bases – essentially the building blocks of DNA.  
 
Currently, DNA sequencing is mostly done through optical or chemical methods. The optical method involves tagging DNA samples with chemicals that cause different neuclotide bases to give off different levels of fluorescence.  
 
The machines that carry out this work, however, are very large and cost about US$10 million (S$14.3 million) each.  
 
During the chemical method, DNA molecules are attached to microbeads, which are then distributed into wells on the surface of a chip. The wells are then flooded sequentially with each of the four A, T, C and G neuclotides. Whenever the DNA on the microbead incorporates the neuclotide, it releases hydrogen ions. Sensors read the changes in each well’s power of hydrogen, or pH, value to identify the DNA’s neuclotide bases. 
 
The machines used in the chemical method, however, cannot tell whether a microbead was deposited into a well. Even if a well is accidentally empty, the machine will still report a pH value for it due to unwanted signals from neighbouring wells, causing inaccuracies in the DNA sequencing. 
 
The EEE researchers’ sequencer uses the chemical method, but adds a photodiode which looks for shadows cast by the microbead in each well under a white light source. If there is no shadow – and hence no microbead – the sequencer does not report a pH value for that well. 
 
The EEE technology is also more accurate and able to determine pH values down to 0.01 pH resolution, compared to the traditional chemical method’s 0.1 pH resolution. 
 
Professor Yu Hao from EEE added that the sequencer, which is a 1cm-by-1cm integrated circuit chip, costs just a few hundred dollars each. He said: This will be a boon to cancer patients and people fighting other diseases."
 

 


By Prof Yu Hao School of EEE


 
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