GENETICS 



the halfway class and the least numbers at the two 

 extremes. In this instance six out of sixteen individu- 

 als of the second generation theoretically present a 

 perfect "blend" between the original brown- and white- 

 chaffed grandparents, although complete segregation 

 has actually occurred. 



The same explanation holds true as displayed in 

 Figure 39 for the trihybrid case of red- and white- 

 kerneled wheats in which only one white-kerneled to 

 sixty-three red-kerneled individuals appear in the sec- 



000 + e o=0o0e0o 



Pure red -f- white =3 Hybrid red 



FIG. 40. The result of crossing white wheat with trihybrid red 



wheat. 



ond filial generation. The number of red determiners 

 in each zygote is indicated by the figure at the bottom 

 of each square. The large screw-head symbols with 

 vertical, horizontal and diagonal slots each represent 

 an independent determiner for red kernel, while the 

 small screw-heads symbolize the absence of each of 

 these determiners, or white kernel. When the pure 

 strain of red-kerneled wheat is crossed with a pure 

 strain of white-kerneled wheat, the first generation is 

 all a heterozygous red of a somewhat lighter shade 

 than the original pure red strain as shown diagram- 

 matically in Figure 40. 



When plants of this heterozygous sort are crossed 

 together, they yield plants producing red-kerneled and 

 white-kerneled wheats in the proportion of sixty-three 

 to one. The sixty-three kinds of red wheats are of 



