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From: werner@aecom.YU.EDU (Craig Werner)
Newsgroups: sci.bio
Subject: Re: C. elegans
Message-ID: <1055@aecom.YU.EDU>
Date: Fri, 8-May-87 15:33:30 EDT
Article-I.D.: aecom.1055
Posted: Fri May  8 15:33:30 1987
Date-Received: Sun, 10-May-87 03:56:06 EDT
References: <1055@thebes.UUCP> <9576@duke.cs.duke.edu> <1640@zeus.TEK.COM> <1044@sigi.Colorado.EDU>
Organization: Albert Einstein Coll. of Med., NY
Lines: 37

In article <1044@sigi.Colorado.EDU>, eddy@boulder.Colorado.EDU (Sean Eddy) writes:
> In article <872@bgsuvax.UUCP> gagen@bgsuvax.UUCP (kathleen gagen) writes:
> >In article <1640@zeus.TEK.COM>, dant@tekla.tek.com.tek.com (Dan Tilque;1893;92-789;LP=A;60/C) writes:
> >> 
> C. elegans is not female (except in some sex determination mutants).
> Instead, it is a hermaphrodite...C. elegans hermaphrodites produce
> both oocytes and sperm. I don't think, then, that C. elegans
> is a legitimate exception; in fact, I would not call C. elegans
> reproduction parthenogenesis at all.

	C. elegans has two sexes.  Hermaphrodites (which are both male
and female combined) and Males (which only produce sperm).  Females are
XX, there is no Y chromosome, males are X  (or XO signifying 1 X only),
and arise by a non-disjunction event.
	Most nematodes, on the other hand, have two definite sexes, where
XX is female and X is male.
	
	Sex determination arises in different ways.  In C. elegans, it
is the X/autosome ratio.  If one has half the number of X chromosomes
compared to everything else, one is a male, hermaphroditic otherwise.
	In Drosophila, males are XY, females are XX, on the surface 
the same as mammals, but XXY are female and XYY are male, so it is the
presence or absence of the second X that is important, Y is just a
place-holder.
	In birds, males have the identical chromosome, and it is females
that are hemizygous.  
	In mammals, it is of course, the case that the Y chromosome
contains the signal for sex determination, or at least the primary
signal.

~.

-- 
			      Craig Werner (MD/PhD '91)
				!philabs!aecom!werner
              (1935-14E Eastchester Rd., Bronx NY 10461, 212-931-2517)
                "I refuse to do mental battle with an unarmed opponent."