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Human handedness and scalp hair-whorl direction develop from a common genetic mechanism

  1. Author:
    Klar, A. J. S.

  2. Author Address

    NCI, Gene Regulat & Chromosome Biol Lab, POB B,7th St,Bldg 539, Frederick, MD 21702 USA NCI, Gene Regulat & Chromosome Biol Lab, Frederick, MD 21702 USA Klar AJS NCI, Gene Regulat & Chromosome Biol Lab, POB B,7th St,Bldg 539, Frederick, MD 21702 USA
    1. Year: 2003
  2. Journal: Genetics
    1. 165
    2. 1
    3. Pages: 269-276
  4. Type of Article: Article
  1. Abstract:

    Theories concerning the cause of right- or left-hand preference in humans vary from purely learned behavior, to solely genetics, to a combination of the two mechanisms. The cause of handedness and its relation to the biologically specified scalp hair-whorl rotation is determined here. The general public, consisting of mostly right-handers (RH), shows counterclockwise whorl rotation infrequently in 8.4% of individuals. Interestingly, non-right-handers (NRH, i.e., left-handers and ambidextrous) display a random mixture of clockwise and counterclockwise swirling patterns. Confirming this finding, in another independent sample of individuals chosen because of their counterclockwise rotation, one-half of them are NRH. These findings of coupling in RH and uncoupling in NRH unequivocally establish that these traits develop from a common genetic mechanism. Another result concerning handedness of the progeny of discordant monozygotic twins suggests that lefties are one gene apart from righties. Together, these results suggest. (1) that a single gene controls handedness, whorl orientation, and twin concordance and discordance and (2) that neuronal and visceral (internal organs) forms of bilateral asymmetry arc coded by separate sets of genetic pathways. The sociological impact of the study is discussed.

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