BB 



Bb 



bb 



GENES, MOLECULES AND PROCESSES 



AA Aa aa 



Fj RATIOS 



AS MODIFIED BY 

 GENE INTERACTION 



@ 



Additive 



AB 



Ab 



aB 

 ab 



Rec.Suppressor 



<4) 



Rec.Epistatic 



AB 

 Ab 



^ 



ab 



DOM EPISTATrC 



(D 



Duplicate 



Fig. 38. — Where two genes are segregating in Fj, nine genotypes are expected with 

 the frequencies shown at the top left of the diagram. With dominance of each gene 

 they give four phenotypcs in the characteristic 9:7:3:1 ratio of the centre of 

 the diagram. This ratio may be modified by genie interaction in the six ways shown. 

 Three of these, complementary action, duplicate action and recessive suppressor 



Continued at foot of page i$7 



156 



