142 



GENETICS IN RELATION TO AGRICULTURE 



color in corn. Taking into account the white dominant factor for 

 aleurone coloration, the following genotypes may be obtained: 



W WccPP = white 

 wwCCPP = purple 



wwccPP = white 



wwCCpp = white 

 wwccpp = white 



WCP 



WCp 



WcP 



Wcp 



wCP 



wCp 



wcP 



wcp 



WCP 



WCp 



WcP 



Wcp 



wCP 



wcP 



wcP 



Fio. 65. Ft checkerboard for cross of white (WWCCPP) X white (wwccpp) corn. 

 In the Ft segregation ratio the purple is given first as in Fig. 64. 



The student will be able to figure out many different relations which 

 exist when such races are crossed. In this section only one will be con- 

 sidered as an illustration of the working of such a system. If a white 

 corn, WWCCPP, is crossed with a white corn, wwccpp, the Fi is of the 

 genetic constitution, WwCcPp, and is white on account of the action of 

 W. The F 2 , however, shows some purple grains as will become apparent 

 from a study of the accompanying checkerboard, Fig. 65. In F 2 such a 

 hybrid segregates in the ratio 55 white : 9 purple, and in F 3 the families 

 show the segregation ratios indicated in the proper squares of the checker- 



