Assignment: Sequencing a person’s genome

Assignment: Sequencing a person’s genome

Assignment: Sequencing a person’s genome

Ten years ago, it cost billions of dollars to map a single human genome. Today, it’s about $20,000 and likely to get even cheaper. If the average consumer can afford to have her own genetic map drawn up, what will it mean for medicine and how we approach our health care?

In early 2008, Henry Louis Gates Jr. stepped off his flight at LaGuardia Airport and began the process of having an elaborate set of blueprints drawn up: the map of himself, his entire human genome.

The Harvard professor of African American studies had at the time just hosted PBS’ successful miniseries, African American Lives 1 & 2. The miniseries, which Gates jokingly calls “Roots in a Test Tube,” traced the genealogical and genetic heritage of prominent figures and celebrities such as Oprah Winfrey, Morgan Freeman, Tina Turner and Chris Rock.

Also on Gates’ flight were officials from the Cambridge, Massachusetts-based genetics company Knome, who told Gates they were interested in working with him on other projects involving DNA testing. Already prompted by the miniseries’ fans to do a show about all Americans, Gates told the Knome representatives that this time he wanted to make a PBS series based on testing the full DNA (or “genome”) of some of his guests.

Every living thing on Earth is built from instruction manuals—an organism’s genes—found inside its cells. The complete set of instruction manuals is called a genome. For humans, the complete set is 6 billion characters long. We all inherit half of our body’s instruction manual (3 billion characters) from our mother and half from our father. When these strands bond together, the connections create units of information called “base-pairs.” Base-pairs can take on one of four values, signified by the names of the molecules from which they’re made: A, C, G or T.

Sequencing a person’s genome means discovering the value of all 3 billion DNA base-pairs—every A, C, G and T—in your body’s instruction manual. It’s the full host of biological blueprints that encodes uniquely who you are.

In 2003, only one human genome had been sequenced in the world, and it cost 50 cents per character. Today, just seven years later, the price has dropped to an astonishing 1/300,000 of a dollar per character. Within two to four years, because of rapidly advancing technology and economies of scale, the price is expected to fall by another factor of 10 or more—bringing the total cost of a full genome down to about $2,000.

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The era of affordable genomes hasn’t yet arrived, but it isn’t far off—and mapping personal genomes at the price point of a laptop computer will change the face of medicine and, in a sense, the world.

For his 2009 series Faces of America, Gates traced the genealogical and genetic heritage of guests such as Eva Longoria Parker, Yo-Yo Ma, Meryl Streep, Stephen Colbert, Dr. Mehmet Oz and figure skater Kristi Yamaguchi. And, although Gates wanted to do full genomes of two of his guests, his scientific advisers recommended instead sequencing the genomes of both Gates and his father, 97-year-old Henry Louis Gates Sr. (Scientists hadn’t yet sequenced any African American’s genomes, nor had they sequenced a father-son pair.)

In fact, perhaps the most heart-wrenching moment in Faces of America comes when the program’s genetic experts subtract Gates Sr.’s 3 billion DNA base-pairs from Gates Jr.’s genome. And there, in bold blue and yellow lines, lies the stark genetic outline of the younger Gates’ mother, who died in 1987. “I put my father in this series,” Gates says. “And the big shock is, I got my mother back.” What Gates discovered about his mother was largely symbolic. He, like everyone, carries the blueprint of each of his parents inside his every cell for every moment of his life.

However, Gates also learned a boatload of information about his own life and health. A person’s genome carries crucial information about individual weaknesses to disease, susceptibility to various cancers, the effectiveness and ineffectiveness of various drugs and, ominously, some of a person’s more likely ultimate causes of death.