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"It is likely that there are many relatively weak genetic factors in handedness, rather than any strong factors, and much bigger studies than our own will be needed to identify such genes unambiguously," says John Armour. (Credit: ed_needs_a_bicycle/Flickr, font by Vernon Adams)

handedness

Genome search still can’t explain lefties

New research rules out a “strong genetic determinant” in influencing left- or right-handedness.

The researchers conducted a twin study examining the whole genome—which contains hereditary information—of nearly 4,000 subjects from the London Twin Research Unit to compare left- and right-handed participants.

Their findings are published in the journal Heredity.

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The study was unable to find a strong genetic factor in determining handedness. If there was a single major genetic determination of handedness, there should be a detectable shift between left- and right-handed people in the frequency of variants in that part of the genome—and this isn’t the case.

Study author John Armour, professor of human genetics at the University of Nottingham, says: “There should be a detectable shift between right- and left-handed people because modern methods for typing genetic variation cover nearly all of the genome. A survey that compared the whole-genome genotypes for right- and left-handed people should leave such a gene nowhere to hide.”

Despite the absence of a strong genetic factor, it is widely believed that handedness is not only a matter of choice or learning. This study suggests, therefore, that genetic factors in handedness must be relatively weak and subtle, which has ramifications for future studies.

“It is likely that there are many relatively weak genetic factors in handedness, rather than any strong factors, and much bigger studies than our own will be needed to identify such genes unambiguously,” says Armour. “As a consequence, even if these genes are identified in the future, it is very unlikely that handedness could be usefully predicted by analysis of human DNA.”

Angus Davison of the University of Nottingham and Chris McManus of University College London also contributed to the study.

Source: University of Nottingham

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