THE MECHANISM OF HEREDITY 



YR GW 



'- 'YR 



£g£ ^YR 



YW 

 YW 



GR 

 GR 



GW)*gi s 



GW}sk'-" 



Fig. 2. Diagram to illustrate inheritance of two pairs of Mendelian characters, 

 viz., yellow-green and round-wrinkled peas. The 16 small squares represent the com- 

 position of the 16 F 2 peas ; viz., 9 YR, 3 YW, 3 GR, 1 GW. 



In each animal or plant there are in general two of each kind of 



chromosomes. 3 One of each kind has come from the father, one from 



the mother, at the time of fertilization (Fig. 3, a). A hybrid likewise 



s Except in those eases where the male has one less chromosome than the 

 female. In such cases the single sex chromosome of the male has no mate. 



