roller males

Leon Avery leon at EATWORMS.SWMED.EDU
Mon Feb 6 18:29:57 EST 1995


> With regard to the observation that crossing males into
> hermaphrodites carrying a roller array gives an excess of roller
> males to roller hermaphrodites: This suggests that the array is
> causing nondisjunction of the X (and probably other) chromosomes in
> the hermaphrodite.  This predicts that some of your roller F1 males
> in fact carry the X chromosome from their father rather than their
> mother (testable by using males that carry an X-linked marker).  You
> also then might expect to see XXX animals (Dpy), and, if other
> chromosomes are also undergoing nondisjunction, occasional lethality
> in the F1 caused by aneuploidy. Has anyone looked for such effects?
> Lisa Kadyk

This phenomenon has actually been known for many years now, and was
discovered with free duplications made by conventional mutagenesis.  I
think it was first described by Jonathan Hodgkin, but it may have been
Bob Herman.  It isn't caused by nondisjunction.  What's happening is
that the duplication is disjoining from the single X.  Similar things
are seen in Drosophila, and used to be explained by "distributive
pairing", although I've heard no one believes in that any more.  The
bias is around 1:3 X;Dp sperm to sperm carrying only the Dp.  In
hermaphrodites, where all chromosomes are paired, all disjoin normally
and the Dp segregates randomly.  One might expect that a Dp would
segregate towards a large Df in hermaphrodites.  I don't know if
that's ever been looked at.

-- 
Leon Avery					   (214) 648-2420 (office)
Department of Biochemistry			            -2768 (lab)
University of Texas Southwestern Medical Center             -8856 (fax)
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