110 



GENETICS 



Phenotypes 



Genotypes 



9SY 



SYSY 



3 SO 



SGSG 



3WY 



WYWY 



already seen, is phenotypically 3:1. This expected 

 ratio corresponds essentially with the actual results 



FIG. 18. Diagram to illustrate the possible combinations arising 

 in the second filial generation (F 2 ) following a cross between 

 yellow-smooth, YS, and green-wrinkled, G^V, peas. 



which Mendel obtained in crossing smooth-yellow and 

 wrinkled-green peas. 



Figure 18 presents a graphic representation of the 

 different combinations resulting from a dihybrid cross 

 following the checkerboard plan used in Figure 16 

 to illustrate monohybrids. 



The nine genotypes and four phenotypes which 



