RP11, scientists later surmised, was probably African American himself, but the problem of using one reference genome to represent the whole human population still holds true. This is especially true in people of African descent, as their high genetic diversity means their DNA is more likely to not match up to the reference genome. If you’re only comparing against the reference genome, “you’re never going to find that missing piece,” says Tina Graves-Lindsay, a geneticist at Washington University of St. ![]() Perhaps they code for novel, interesting mutations related to disease that studies using the reference genome overlooked. Now the question is what those 300 million previously overlooked letters of DNA contain. ![]() But when she went back and combed through all of her code, she couldn’t find any errors. “I thought I must have done something wrong,” says Sherman. Sherman and Salzberg found nearly 300 million missing letters in 125,715 separate DNA segments-much more than they expected. Smaller studies have found enough novel DNA sequences that they estimated there are as many as 40 million letters that can appear in the human genome, but are not in the current reference genome. In other words, their research presented an opportunity to study the diversity missing from the reference genome. “It occurred to me we had this very genetically diverse group,” says Salzberg. That study includes people living in West Africa, North America, South America, and the Caribbean. Sherman’s adviser, Steven Salzberg, collaborates with researchers studying the genetics of asthma in people of African descent. “We wanted to look at what’s in the pieces we’re ignoring,” says Rachel Sherman, a computational biologist at Johns Hopkins University who is the lead author of the study. Read: 23andMe wants its DNA data to be less white. If a new segment pops up-one that doesn’t match anything in the reference genome-the algorithms don’t know what to do. Algorithms use the reference genome to tell them where to put each segment. Currently, DNA sequencers work by chopping up a genome into segments that are individually “read” and then assembled like a jigsaw puzzle. Some of these newfound segments of DNA could represent new genes that were previously overlooked.Īfricans collectively are far more genetically diverse than people in other parts of the world, so their DNA is especially likely to differ from the reference genome. ![]() Every person’s genetic code is unique, so using just one reference genome-most of it from one person-to stand in for all of humanity has introduced subtle biases into genetics research.Ī new study of DNA from people of African descent shows just how much the reference genome is missing: Scientists found across the 910 people in their study 300 million letters of DNA that are not in the reference genome. ![]() It’s become a “reference genome,” the standard against which practically every human whose DNA has been sequenced is compared. Since then, that first human genome has been continually refined. The rest came from about 50 other volunteers. Ultimately, 70 percent of the Human Genome Project’s DNA came from RP11. And it happened that, as the race to complete the first human genome heated up, it was RP11’s sample that was ready to be sequenced first. The ad RP11 answered turned out to be for the Human Genome Project. He did not leave a name, as the researchers who took his blood wanted to keep things anonymous. He agreed to give 50 milliliters of blood. In March 1997, a man answered an ad in The Buffalo News.
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