308 



THE CONTINUITY OF THE RACE 



was concealed by the large number of genes involved. Suppose that 

 the red color in the wheat is due to three pairs of genes, AA BB CC, and 

 each of these genes contributes one-sixth of the total redness. Then A a 

 bb cc, aa Bb cc, or aa bb Cc will produce a kernel one-sixth as red as an 

 AA BB CC individual, AA bb cc, Aa Bb cc, Aa bb Cc, etc., will produce 

 a kernel one-third as red, etc. In the original cross, the red variety has 

 the constitution A A BB CC, the white variety the constitution aa bb 

 cc, and the pale red Fi individuals have the constitution Aa Bb Cc. The 

 gametes of the Fi will be of eight kinds: ABC, ABc, AbC, aBC, Abe, 

 aBc, abC, and abc, and if all possible recombinations occur, 27 genotypes 

 will be produced, as shown in the following diagram. 



1 individual in 64 with 6 genes for red 



6 individuals in 64 with 5 genes for red 



15 individuals in 64 with 4 genes for red 



20 individuals in 64 with 3 genes for red 



15 individuals in 64 with 2 genes for red 



6 individuals in 64 with 1 gene for red 



aa 



bb 



cc 



1 individual in 64 with genes for red 



Here is a hypothesis that seems consistent with many of the crosses 

 that appear to show a blended inheritance. It explains the rarity of the 

 appearance of either parent type in the F 2 , the fact that the F 2 is much 



