May 12, 2014 - Research

23andMe scientists improve method for finding relatives

Two 23andMe scientists have improved a long-used method for detecting shared DNA segments.

Researchers use this method to study everything from whether two people are related to human demography to the heritability of disease.


The two computational biologists – Eric Durand, Ph.D., and Cory McLean, Ph.D. – recently published their findings in the journal Molecular Biology and Evolution. The pair also made their algorithm, HaploScore, publicly available.

Previous studies have used computer simulations to determine the accuracy of established methods for determining identity-by-descent (IBD). Still, Eric and Cory are the first to test those methods with actual human data.

When they scrutinized current methods, they found that the algorithms produced many errors.  S0 Eric and Cory created a better and more accurate method for determining IBD. Their now open-source method is called HaploScore.

“HaploScore will allow all researchers to more accurately identify genetic relationships between distantly related individuals,” said Cory.

Identity by Descent

Researchers use methods for determining IBD to identify shared segments of DNA. They look at IBD in many aspects of genetic research. They used it to determine the “relatedness” of any two individuals. The longer the shared segment, the closer the relationship. Up to now, studies of the accuracy of the methods for determining IBD have been done with simulated data.

When Eric and Cory used the popular IBD detection method GERMLINE on data from about 3,000 biological parent and child “trios.” They found a false positive rate of 67 percent for small segments. HaploScore improves the accuracy of short IBD segment detection, allowing researchers to look at much shorter segments of shared DNA to determine relatedness. Segments of DNA are measured in units called centiMorgans.

Eric and Cory’s new method allows for more accurate IBD determination on segments in the range of 2 to 4 centiMorgans. As more people are genotyped or have their DNA sequenced, having an accurate method for determining IBD will be increasingly important.

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