Chapter VIII 



SEX-LIXKED IXHEKITAXCE 



When we follow the history of pairs of chromo- 

 somes we find that their distribution in successive 

 generations is paralleled by the inheritance of ]Men- 

 delian characters. This is best shown in the sex 

 chromosomes (fig. 44) . In the female of Drosophila 

 there are two of these chromosomes that are called 



Diploid Nuclei XX 



Gametes 



X Y 



Fertilization 

 Zygotes 



Fig. 44. — Diagram showing the di.stri])uti()ii 

 of the sex chromosomes from parents to off- 

 spring. 



X-chromosomes ; in the male there are also two, but 

 one differs from those of the female in its shape, and 

 in the fact that it carries none of the ordinary genetic 

 factors. It is called the K-chromosome. 



The inheritance of a pair of characters whose 

 genes lie in the A^-chromosomes is shown in figures 



