Most accurate genetic map to date is published

21 July 2011

You can’t use this map to find out where you’re going, but it does tell us a lot about where we came from: it’s the world’s most advanced human genetic map, as constructed by a consortium of scientists led by researchers at the Wellcome Trust Centre for Human Genetics, University of Oxford, and Harvard Medical School.

Published in 'Nature' today, it is also the first genetic map to be made using data from African Americans. It reveals surprising differences between African and non-African populations in the way our genetic information is subject to change. As well as yielding insights into genes associated with certain diseases, the map will help us understand the evolution of the human race.

While a genome sequence shows the order of the 3 billion bases that make up our DNA, a genetic map shows which regions of the genome are most prone to change during the reproductive cycle. As sperm and egg cells are made in our bodies, a process called recombination takes place.

Recombination swaps genetic material between chromosomes, which can alter genes or change the order they are in. In effect, it shuffles our DNA, ensuring healthy levels of genetic variation in the population but sometimes leading to disease.

Recombination does not happen everywhere in the genome but is focused at 'hotspots'. Common to these hotspots is a specific motif: a string of DNA bases that can bind an enzyme critical for recombination. Without this motif, the enzyme cannot bind and initiate recombination.

The new genetic map identifies the recombination hotspots in African Americans and reveals a new DNA motif that binds a different version of the recombination enzyme: one that is almost exclusive to people of African ancestry.

Part of the ‘African American Map’, which is published today.

Lead author Dr Simon Myers, of Oxford University and the Wellcome Trust Centre for Human Genetics, said: "More than half of African Americans carry a version of the biological machinery for recombination that is different than Europeans. As a result, African Americans experience recombination where it almost never occurs in Europeans."

Dr Myers and colleagues had previously discovered the DNA motif that flagged recombination hotspots in studies of European populations. But it only accounted for two-thirds of recombination in African Americans. The other one-third of recombination was associated with the new motif.

Anjali Hinch, a postgraduate student at the Wellcome Trust Centre for Human Genetics and first author on the paper, said: "The landscape of recombination has shifted in African Americans compared with Europeans."

This map will help researchers to understand the roots of congenital conditions, especially those that occur more frequently in African Americans, because it maps so precisely the locations of genes that are prone to recombination and, as a result, are often involved in disease. It will also yield genetic information that can help to trace human variation and evolution over thousands of years of history.

Top image: A map of the world (coloured lithograph). Credit: Wellcome Library, London.