GENETIC SYSTEM: RELATION TO CHARACTERISTICS llj 



Table 2, for Inheritance Depending on Two Pairs of 



Autosomes 



AB AB AB AB 



AB(i) Ab(6) aB(7) ab(5) 



Ab Ab Ab Ab 



AB(6) Ab(2) aB(5) ab(8) 



aB aB aB aB 



AB(7) Ab(5) aB(3) ab(9) 



ab ab ab ab 



AB(5) Ab(8) aB(9) ab(4) 



But, as win be observed, not all these 16 are diverse; 

 thus ABAb Is the same In constitution or genotype as 

 AbAB. If we number the different combinations, and give 

 the same number to those that are alike, as Is done (In 

 parentheses) In the table, we find that there are nine dif- 

 ferent combinations or genotypes. That Is, two parents 

 that are both ABab produce offspring of nine different con- 

 stitutions or genotypes. In the relative proportions given in 

 the table. When the parents differed In but one pair of 

 characters there were but 3 different combinations. When 

 there are two pairs the number is 3^, or 9. 



These nine different combinations will manifest the domi- 

 nant characters A or B, in all cases where an A or B is 

 present (whether present once, as A, or twice, as AA) ; 

 they will manifest the recessive characters a or b m all cases 

 in which a or b is present twice, no corresponding capital 

 letter being present. Collecting together these different 

 types, we find the different characteristics to be manifested 

 in the following proportions of the zygotes : 



9AB H- 3Ab + 3aB + lab 



That is, 9 out of 16 are dominant for both pairs of 

 characters, 3 are dominant for A, recessive for b; 3 domi- 

 nant for B, recessive for a, and i out of 16 is recessive for 



