182 GENETICS 



The numbers in the squares in Figure 37 indicate how 

 many times a brown determiner is present in each 

 zygote. It will be seen that only one out of the sixteen 

 possibilities lacks a brown-chaff factor, and this one will 



43210 



Number of doses of the brown determiner 



FIG. 38. The distribution of the sixteen possibilities resulting 

 when two similar determiners (brown-chaff) act together as 

 a dihybrid. 



consequently produce only white chaff, while the re- 

 maining fifteen possibilities, each of which has at least 

 a single determiner for brown, will all yield brown 

 chaff. 



The brown-chaff factor, moreover, is present in 







