Calico cats vs. Chimeric mi

[Joanne_Ownbey at CBRC.MGH.HARVARD.EDU]

                      Calico cats vs. Chimeric mice?
I now understand how one can have a male calico cat.  What confuses me is
how can one get a female chimeric mouse made from presumably an XX
blastocyst and known XY ES cells that can pass on the ES cell "trait" to
the next generation?  The problem that I'm having is that if XY ES cells
are contributing in any way to the gonad shouldn't you get a male
phenotype.  And if the ES cells are not contributing to the gonad then the
"trait" shouldn't be passed on to the next generation.  Any help in
explaining this would be greatly appreciated.

Thanks in advance,
Joanne