MARY LOUISE KELLY, host:

Now, if one day we get a better understanding of our genetic makeup, you may want to thank the people you'll hear about next. Scientists have been trying to figure out DNA, that genetic material that makes us what we are, but it's not easy.

STEVE INSKEEP, host:

Finding a specific gene with the information we have now would be a little like taking one of those folding interstate highway maps and with no more information than that trying to locate a specific house in Topeka, Kansas. Now two independent teams have come up with a new map that should make finding genes easier.

NPR's Joe Palca reports.

JOE PALCA: Researchers search for genes because genes help explain diseases. But you need a map, and the trick to making a genetic map is making road signs in the DNA to tell you where you are.

John Novembre is a geneticist at UCLA. He says one way to make road signs is to look for what are called recombination events.

Dr. JOHN NOVEMBRE (UCLA): What you're trying to do is identify locations where along the chromosome the DNA that a person inherits from their mother is different from the DNA that they inherited from their father.

PALCA: And that's the recombination event, where a strand of DNA has switched from one parent's DNA to the other.

Dr. DAVID REICH (Harvard Medical School): The recombinations don't occur evenly across our genetic material. They occur in very small hot spots.

PALCA: David Reich is a geneticist at Harvard Medical School. These specific hot spots become the road signs along the chromosomes researchers use to create the new genetic maps.

If all this is a scary reminder of what you didn't quite understand from high school biology, don't worry. The point is, the map helps geneticists find their way.

Reich and his colleagues at the University of Oxford in England are publishing their map in Nature. Novembre and his UCLA colleagues published in Nature Genetics.

What makes these genetic maps particularly interesting is they were developed using DNA from African-Americans. Most maps created so far are based on DNA from people of European ancestry. Reich says using African-American DNA revealed something unexpected.

Mr. REICH: There's a family of about 2,500 hotspots of recombination that are active in people of West African ancestry like African-Americans, which are almost completely inactive in people of non-African ancestry.

PALCA: Finding these 2,500 hotspots could be particularly helpful for finding genes for diseases that are more common in African Americans. David Wegmann is a collaborator of John Novembre at UCLA.

Mr. DAVID WEGMANN (UCLA): Researchers need maps that are matching the ancestry of their sample relatively closely, and so we're hoping that this map can actually serve as a great tool for disease mapping studies in African-Americans.

PALCA: It hasn't always been easy to recruit African-Americans to research studies. Herman Taylor heads the Jackson Heart Study, an effort to follow the heart health of some 5,000 African-Americans.

Mr. HERMAN TAYLOR (Jackson Heart Study): History has shown that African-Americans participating in large studies like ours didn't always get the most benefit of participation.

PALCA: But Taylor believes that will not be the case with the new mapping study. He's a co-author on the Harvard-Oxford study.

Mr. TAYLOR: Studying African-American genetics gives unique information about African-Americans, but also it is uniquely informative to genetics of the family of man.

PALCA: Because Africa is thought to be the place where all modern humans originally came from, so DNA from African people tells the first chapter in the story of modern human genetics.

Mr. TAYLOR: I think the people in the Jackson Heart study recognize that they have an important contribution to make.

PALCA: And with time, Taylor thinks their contribution will bring tangible benefits.

Joe Palca, NPR News, Washington.

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