Appendix E 



441 



Problem 3. 



The cases Which have been considered hitherto show perfect 

 dominance of one unit over another. This is not always the 

 case. It frequently happens that the first generation hybrid 

 is intermediate between the two parents, and in the second gen- 

 eration the heterozygote forms differ from either homozygous 

 form. Thus when large, round tomatoes are crossed with small, 

 plum-shaped ones, the FI hybrid is intermediate between the 

 parents. If L represents largeness and (I) small, plum-shaped, 

 then F! hybrids (LI) will not be the same as (LL), but will be 

 distinctly different. The formulae previously given, 2", 3 n , etc., 

 will not hold in cases of incomplete dominance. This will be 

 more fully explained later. Large (L) X small, plum-shaped 

 (/) = LI, an intermediate type of fruit. 



gametes 

 self ed 



POLLEN GRAINS 



EGG CELLS 



LL 



LI 



LI 



Phenotypes = 1 LL; 2 LI; III 

 Genotypes = 1 LL; 2 LI; III 



Problem 4. 

 Intermediate (LI) X Large, round (LL) 



