92 



CHAPTER 7 



A-l B-l 



9W W ^fl W W ("*) WW X 



xxx(j p, x y qp x X X (J 



W fl^^ WW fl ^ 



x OO F x x OCT 



+ 99 W99 



+ + 



W W ( 1 WW 



P, X Y x X X 



w 



w w 

 X Y 



A-2 



+ + 

 P, X X X : 



B-2 



Q w w 



+ + 



^ w wO w w 



Q P,XXqpxXY 



a* 



+ 

 w w 



X Y 





A-3 



99 



B-3 



+ + 



O WW ^_^ W W ("") WW ^ 



p,xx Y xXY U p, x x ; x x y Q 



w 



>99 



w w 

 X Y 



0*0* 



' x->99 



figure 7-3. Three attempts (A-l and B-l, A-2 and B-2, A-3 and B-3) 

 to represent matings A and B in Fig. 7-2 genotypically. Shaded genotypes 

 must he incorrect. 



X"X" sons and X"Y"' daughters, all 

 dull-red-eyed, as found. The reciprocal 

 cross (Figure 7-3, B-l), therefore, is white 

 9 X"Y" by dull-red $ X W+ X M '\ The 

 Fi daughters (X"'*Y W ) are expected to be 

 dull-red-eyed, as found. The Fi sons 

 (X"*X" '), also expected to be dull-red-eyed, 



are, however, actually white-eyed. There- 

 fore, we must reject this particular hypoth- 

 esis for correlating sex chromosomes and eye 

 color genes. 



So let us assume the reverse situation — 

 that females are XX and males XY. The 

 same crosses are represented now as dull-red 



