384 



CHARACTER EXPRESSION OF GENES 



of genes c and c' to be involved. The ab gametes can 

 then be either abc or abc'; i.e., there are twice as many 

 kinds of ab gametes as before. The same thing is true 

 for the other kinds. Thus each additional pair of charac- 

 ters and genes for which a plant or animal is hybrid 

 doubles the number of different kinds of gametes it can 



Njhe F "hybrids^ 

 Vermilion/femaje Red ftfnale ^^ermilion^male White sale 



Fio. 114. — Red-Eyed Hybrids produced by crossing white-eyed 

 and vermilion parents. The f'l male is vermilion because he receives 

 his single X-chromosome from his mother. The F\ female is red-eyed 

 because she receives an X-chromosome with the normal red factor V 

 from the father and another with the normal red factor W from 

 the mother. The results of interbreeding the F\ males and females 

 is shown in the lower row of the diagram. 



produce. Or, in general terms, an organism hybrid for 

 n pairs of independent genes and characters can produce 

 2" kinds of gametes. 



