CHAPTER IX 



NEO-MENDELISM (Concluded) 



Thus far we have based our considerations on the 

 rather simple theoretical mechanism of inheritance which 

 was explained in connection with Mendel's law. We 

 shall now consider some well established facts of inherit- 

 ance which will oblige us to enlarge somewhat our 

 theoretical mechanism. 



8. Coupled and antagonistic characters. — The 

 classic illustration of coupled characters was brought 

 to light by Emerson (i) during breeding experiments 

 with corn. His material included a strain with red 

 grains and red cob. This strain, when crossed with 

 another having white grains and white cob, gave an F; 

 generation with red grains, and red cob. This indicated 

 that red was dominant over white in both grain and cob; 

 and since the Fa generation gave the orthodox 3:1 

 ratio (3 reds and i white) the obvious conclusion was 

 that redness in both grain and cob is due to a single 

 determiner. 



Other breeding experiments, however, gave a differ- 

 ent aspect to the situation. It was found that there 

 are races of corn with red grains and white cobs, and 

 others with white grains and red cobs. It is evident, 

 therefore, that redness in grain and cob is due to two 

 separate determiners. 



Let us consider a possible theoretical explanation of 

 these two apparently contradictory situations. The red 



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