Grex Science Conference

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Grex Science Item 96: Handedness
Entered by rcurl on Sun Dec 21 18:17:11 UTC 2003:

Apparently the genetics of handedness - right or left - has been
elucidated.  According to an article in American Scientist, it is
controlled by a single gene with two alleles. The right-handed allele is
dominant so that if a person has either one or both alleles right-handed,
that person is right-handed. However if a person has two recessive
alleles, whether they are right or left handed is a 50-50 random outcome. 

This account for the inheritance of handedness. One aspect of that that
had not been understood was the fact that two left-handed parents could
have right-handed offspring.

The matter is even more intriguing as another trait is related to this -
the direction in which the whorl of hair on the head turns (moving outward
from the center of the whorl). This is clockwise in persons right-handed
because of a dominant allele, but can be either right or left handed in
persons right or left handed because of two recessive alleles. The
handedness of the whorl is also a 50-50 trait independent of that of the
hands in such a case.

5 responses total.

#1 of 5 by rcurl on Sun Dec 21 18:28:08 2003:

My parents were right-handed and so am I, but my brother is left handed. 
I also have a right-handed whorl. This means that both of my parents had
to have been carrying the recessive "neutral" allele, either singly or
doubly. Both my wife and daughter are right-handed with right-handed
whorls. This still, however, does not settle the case of whether I carry
none, one, or both alleles of "neutral". It does, however, settle it that
my brother has two "neutral" alleles. 

What is your situation and does it resolve your genetic status?

#2 of 5 by eprom on Mon Dec 22 00:29:01 2003:

haha...I'll have to check my whorl in the mirror tonight...I'm a lefty

#3 of 5 by keesan on Mon Dec 22 04:30:30 2003:

Rightie, clockwise whorl.  All my relatives are righties.  rightys?

#4 of 5 by prp on Sun Aug 15 17:18:08 2004:

Given 10% as the proportion of left-handed people, it works out
that 44.72% of the alleles out there are neutral, and 55.28% are
the right handed one.

That means that either the right-handed allele is more adaptive,
or the neutral allele is quite a bit newer.  I know that mice
develope a domanant paw, but don't know one side is more common
than the other.

Does anybody know primates tend to be right-handed?

#5 of 5 by rcurl on Mon Aug 16 00:47:50 2004:

http://www.abc.net.au/rn/science/ss/stories/s11027.htm

" Professor Lesley Rogers' research has found that lower primates are more
likely to be left-handed and the higher primates have a right-handed bias.
She has been working with a long-established colony of Marmosets at the
University of New England in Armidale, NSW. Her research, and that of others
in America has shown that populations of primates have definite preference
for handedness and that right-handed marmosets are more adventurous and tend
to rush into new surroundings, sometimes disappearing in the jungle and being
unable to find their way back, while the left-handed marmosets hang back and
are more fearful and less adventurous. This research may be helpful in
rehabilitating rare species of marmosets. "

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