Table 1.

Genotypes of the 3 Crosses

Groups	Genotypes	Shorthand	Gonadal sex	NPX	NPY	PAR (Sts)	Sry	Xp	Xm	XPA
Cross A: MF1 XX♀ × ♂XY− (Sry+) (produces the 4 core genotypes)
1♀	XX	XXF	F	2	0	2	0	1	1	2
2♀	XY−	XYF	F	1	1	2	0	0	1	1
3♂	XX(Sry+)	XXM	M	2	0	2	1	1	1	2
4♂	XY−(Sry+)	XYM	M	1	1	2	1	0	1	1
Cross B: MF1 XX♀ × XY−Y*X(Sry+) ♂
1♀♂	XX	XX	Both	2	0	2	1♂ or 0♀	1	1	2
2♀♂	XY*X	XO + PAR	Both	1	0	2	1♂ or 0♀	0	1	2
3♀♂	XY−	XY	Both	1	1	2	1♂ or 0♀	0	1	1
4♀♂	XO	XO	Both	1	0	1	1♂ or 0♀	0	1	1
5♀♂	XXY*X	2X + PAR	Both	2	0	3	1♂ or 0♀	1	1	3
6♀♂	XY−Y*X	XY + PAR	Both	1	1	3	1♂ or 0♀	0	1	2
7♀♂	XXY−	XXY	Both	2	1	3	1♂ or 0♀	1	1	2
Cross C: XX♀ × XY* ♂ (XY* model)
1♀	XO	XO	F	1	0	1	0	0	1	1
2♀	XY*X	XO + PAR	F	1	0	2	0	0	1	2
3♀	XX	XX	F	2	0	2	0	1	1	2
4♂	XY*	XY	M	1	1	1	1	0	1	2
5♂	XXY*	XXY	M	2	1	1	1	1	1	2

Abbreviations: NPX, nonpseudoautosomal region of the X chromosome; NPY, nonpseudoautosomal region of the Y chromosome; Xp, X chromosome inherited from the father; Xm, X chromosome inherited from the mother; XPA, small PAR-adjacent region of the NPX region containing a small number (∼6–8) coding genes, variably present as an extra copy in some of the progeny in of XY* mice (Figure 1). In the XY* model, 3 regions of PAR are shown in Figure 1, which are variably present on the aberrant chromosomes. This table tallies the numbers of PAR region C shown in Figure 1, which contains steroid sulfatase (Sts), the only known PAR coding gene in mice. The X^Y* chromosome in group 5 of cross C is the fusion of NPY and NPX with an aberrant intervening PAR. The Y⁻ chromosome is from strain 129 (11). In cross B, genotypes 4 and 5 are rare.