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From: eddy@boulder.UUCP
Newsgroups: sci.bio
Subject: Re: Human asymmetry
Message-ID: <865@sigi.Colorado.EDU>
Date: Thu, 2-Apr-87 10:59:42 EST
Article-I.D.: sigi.865
Posted: Thu Apr  2 10:59:42 1987
Date-Received: Sat, 4-Apr-87 19:47:28 EST
References: <586@batcomputer.tn.cornell.edu>
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Reply-To: eddy@beagle.Colorado.EDU (Sean Eddy)
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Organization: University of Colorado, Boulder
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{The question has to do with the origins of left/right asymmetry 
in higher eukaryotes.

The answer has to do with the microtubule/cilia/flagella system.  
Mutations that cause immobile cilia (Kartegener's syndrome) lead
to sterility (since the sperm cannot swim and the oviduct can not 
transport oocytes) and respiratory problems, since the surface of 
the lung is not kept clear of mucus, etc.

In addition, approximately 50% of these people have their internal
organs reversed.  Since these mutations appear to affect only 
cilia/flagella (differently sized versions of the same microtubule-
based structure), it appears that it is either the asymmetric beat wave
form of these subcellular organelles or some asymmetric aspect of
microtubules themselves that determines organismic asymmetry.  It seems
unlikely that defect is in microtubules themselves, since microtubules
are intimately involved in essential functions (like mitosis), therefore
a likely guess is that ciliary beating early in the developing embryo
establishes a handedness for the embryo.

Enough biology for the moment, anyone seen a good movie lately?