sex determination

Joe Kunkel joe at bio.umass.edu
Wed Apr 28 18:52:44 EDT 1999


Dalius,

While it is certainly correct that the sex of leps is determined via sex
chromosomes, that does not tell us when those sex chromosomes act to
achieve that sex in each tissue.  In both Drosophila (fly) and leps,
gynandromorphs can form by a non-disjunction or chromosome loss during
the early cell divisions of the egg.  This can result in the right and
left halves of the animal being of different sex.  Thus _Papilio turnus_
(Tiger swallowtail) with left wings brown and right wings yellow have
been pictured in the literature which undoubtedly resulted from such
chromosomal accidents.  That does not mean that the chromosomes acted at
that early time to determine the sex of the wings.  Experiments
mentioned earlier on Drosophila show that a cascade of genes act in each
tissue at a specific time in development to determine its sexual
phenotype.  The sex of the Drosophila abdominal integument is determined
in the pupal stage.  The sex of its wings is determined in the mid to
late larval stage.

Joe Kunkel  

Dalius Dapkus wrote:
> 
> Dear Andrea,
> 
> I am not a genetic specialist but I know that most of insects have
> such sexual chromosomes:
> females - XX, males - XY.
> But SOME SPECIES of Lepidoptera (I do not know how many) have:
> females - XY, males - XX sexual chromosomes.
> So logically sex is determined after copulation and when an egg is
> formed. I do not know any facts that any other factors could
> determine the sex.
> 
> Dalius Dapkus
> 
> > Hi all,
> >
> > does anybody klnow when the sex of a butterfly is determined? Is it
> > set in the egg right after laing? Or is it possible to change the sex by
> > e.g. temperature after the egg is laid like in some fish?
> >
> > Thanks in advance,
> > Andrea Knebel
> > University Bielefeld,
> > Germany
> >
> >

-- 
--------------------
Joseph G. Kunkel, Professor
Biology Department             joe at bio.umass.edu
University of Massachusetts    http://www.bio.umass.edu/biology/kunkel
Amherst MA 01003


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