Path: utzoo!utgpu!jarvis.csri.toronto.edu!mailrus!iuvax!silver!chiaravi
From: chiaravi@silver.bacs.indiana.edu (Lucius Chiaraviglio)
Newsgroups: sci.bio
Subject: Re: twins
Summary: won't work
Keywords: how not to get monozygotic twins of different sex
Message-ID: <3089@silver.bacs.indiana.edu>
Date: 1 Feb 89 06:45:22 GMT
References: <1046@jimi.cs.unlv.edu> <775@bimacs.BITNET> <1091@asylum.SF.CA.US>
Reply-To: chiaravi@silver.UUCP (Lucius Chiaraviglio)
Organization: Department of Molecular, Cellular, and Developmental Biology at Indiana University, Bloomington
Lines: 21

In article <1091@asylum.SF.CA.US> ayermish@asylum.UUCP (Aimee Yermish) writes:
>Another very long shot on how you could get monozygotic twins to be of
>different sexes:  If they both started out female, but right early on 
>(I mean *really* early on, although I don't know enough about
>developmental bio to say more specifically) one of them had a breakage
>(or maybe a very lucky translocation) in one X chromosome cutting it
>short such that it was for most intents and purposes a Y chromosome.

	Won't work.  If you break an X chromosome in an XX individual you
still get a female, no matter where you break it.  This is because merely
cutting an X chromosome short does not make it a Y chromosome -- a Y
chromosome has different contents than an X chromosome.  If you mess up one X
chromsome badly enough you will cause abnormality (known as Turner's Syndrome,
whose most extreme form consists of the individual having only 1 X
chromosome), but the individual will still be female.

-- 
|  Lucius Chiaraviglio   |  ARPA:  chiaravi@silver.bacs.indiana.edu
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