THE GENERAL ASPECTS OF HEREDITY 23 



colour-blindness. The male, XY, would therefore be 

 colour-blind. Mated with a normal woman, their 

 male children would all be normal. The X chromo- 

 some of the father, however, goes to all his daughters, 



Parents 



XX 



X Y 



Germ cells 



XX X Y 



Zygotes 



XX XYcf 



OXX 



Germ cells 



XX XY 



Zygotes OXX OXX XYCJ" XYd' 



Germ cells 



XX 



XY 



Zygotes 



^XX XX^ XYC? XYC/ 



Fig. 8. — Diagram to illustrate the Inheritance of Sex- 

 Linked Characters through the X-Chromosome. 



who are all, therefore, transmitters of the defect to 

 future generations. With a husband who is normal, 

 they will transmit the defect to half their children 

 of both sexes, as shown in the next two lines of the 



