DNA Sequencing

Cancer is a terrifying diagnosis, but today's patients have a new weapon in their arsenal: DNA sequencing. While cancer symptoms often look alike, their underlying pathology may differ greatly. By analyzing a cancer's DNA, clinicians can identify the mutations that caused the disease and the treatments that would work best.

Cancer is not the only clinical application of DNA sequencing. The technology plays a critical role in identifying rare and hard-to-diagnose diseases. It helps match patients with the best available drugs. It screens newborns with issues for potential causes. Physicians use it to identify bacterial and viral infections. 

This is an unimaginable turn from 25 years ago, when sequencing human genome (all its DNA) cost about $100 million. Today, high-quality sequencing costs between $200 and $500 and the race is on to drop prices below $100. This has transformed sequencing from a laboratory curiosity to a go-to medical tool. 

It took incredible biomedical engineering--and the $3 billion Human Genome Project--to get there. In the beginning, mapping our genome was incredibly time-consuming. It involved cutting a strand of DNA into randomly sized pieces and amplifying (reproducing) enough of them to read. After identifying each segment's chemical makeup, computers looked for overlapping segments to figure out how the pieces might fit together.

It was an unimaginably large jigsaw puzzle. DNA consists of base pairs, two bonded nucleic acids that form one rung on its ladder-like structure. The human genome has 3 billion base pairs. The best technology read only 500 to 1,000 of them at a time. Thousands of people at 20 major sequencing centers in six countries took 13 years to complete the project.

Today, advanced sequencers could read 1,600 genomes in 48 hours. What happened? Early on, National Institutes of Health realized that existing technologies could never sequence genomes fast or cheap enough for everyday use. They started a second project to fund competing, out-of-the-box technologies. The key breakthrough was to eliminate single reactions. Instead, massively parallel systems cut up and sequence the entire genome at once, undertaking millions of reactions at a time. 

The result is a high-speed, low-cost system that is making DNA testing part of everyday medicine.