RED-EYED FEMALE 



377 



WMTTC 



Fig. Ill, — Sex-Linkage. A cross involving the genes red and 

 white eye, which are located in the sex chromosomes. The X-chro- 

 mosomes of the female parent are colored black to indicate the 

 presence of the gene for red-eye and the X-chromosome of the male 

 left white to indicate the white gene. The Y-chromosome of the 

 male is also left blank because it does not contain either gene. The 

 diagram shows that the first generation males and females are both 

 red-eyed because each receives a gene for red-eye. In the second 

 generation all females are red-eyed since they have either one or 

 two chromosomes with the red gene whereas only half the males 

 receive the chromosomes with the red gene. The other half receive 

 a chromosome with the white gene and are white-eyed. 



Morgan, Sturtevant, Muller, Bridges, Mechanism of Mendelian 

 Heredity. Holt. 



