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Archiver > Scotch-Irish > 1998-02 > 0887909198


From: Sharon McAllister <>
Subject: RE: Scottish Left-handedness -Reply
Date: Thu, 19 Feb 1998 12:26:38 -0500


Rob wrote:

> If I remember my genetics class, which I just barely passed so I don't
feel
> overly confident in this response, I think one fraternal twin is always
> left-handed. This is because the twins develop as a "mirror image" of
> each other. Thus, one is always left-handed and the other is always
right-
> handed.

It's been a long time since my college genetics class, too -- but back then
the term "mirror twins" was used to describe the type of identical, not
fraternal, twins who are mirror images of each other. The difference is
very subtle, sometimes just enough to enable friends and family to tell
them apart without knowing how they do it. And, yes -- one is naturally
left-handed and one is naturally right-handed.

As for the incidence of left-handedness in fraternal twins -- I don't know.

Sharon McAllister

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