220 



GENETICS 



a case the heterozygotes, containing the two different modifi- 

 cations of the gene, are either intermediate in character, or 

 approach one of the recessive parents more closely than the 

 other. 



B. The recessive genes in the two parents are not alleles, 

 but are modifications of genes at different loci (figure 47). 



Fl 



Figure 46. Diagram to illustrate inheritance of recessive characters 

 in cases in which the two parents are recessive in genes that are alleles 

 (belonging to the same pair). The offspring (Fi) manifest the re- 

 cessive character. 



In such cases the offspring (Fi ) show, not the recessive char- 

 acters, but the normal or dominant characters. The reason 

 for this is, as shown by figure 3 1, A, that each parent has the 

 dominant allele for the recessive character of the other 

 parent. 



If the two pairs of recessive characters of one parent are 

 bb and those of the other parent are ee, then the parent 

 carrying bb has also the dominant genes EE, while the par- 

 ent carrying ee has the dominant genes BB (figure 47 ) . Thus 

 the two parents are bbEE and BBee. Their offspring (Fi) 

 are therefore BbEe; they have the dominant gene for both 



