io6 



GENETICS 



marked AA In figure 27. Suppose that in different indi- 

 viduals the members of this pair of autosomes produce 

 different effects, as we have seen to be the case with the X- 

 chromosomes of different individuals. And suppose that, 



Parents 



D 



R 



'er«i 



Celli 



Fl Zygotes 



D 



Figure 27. Diagram to illustrate the results of mating dominant 

 and recessive parents (D and R), differing in a single pair of auto- 

 somes, AA and aa. The offspring Fi are all heterozygote domi- 

 nants Aa. 



as in the case of X, one of these effects is dominant, the 

 other recessive. How would such characteristics be in- 

 herited? 



This question must be examined with care. For this pur- 

 pose we may take as an example the different colors found 

 in different varieties of peas, used in the classic experiments 

 of Mendel.^ The yellow seed color of a certain variety is 

 dominant, and results from the constitution of the auto- 



