CHAPTER 35 



Heredity 



Selection has long been used in producing 

 superior animals, such as the beautiful and 

 sensitive race horse, the luxuriously furred 

 blue-ribbon cat at the pet shows, and the 

 pointer with its keen sense of smell. But 

 what is more recent and more important, 

 the knowledge of heredity has been used to 

 produce the prize-winning steer at the fair 

 to be sold for its steaks and roasts, and the 

 golden-eared hybrid corn. 



The knowledge of heredity has made great 

 socio-economic contributions to human wel- 

 fare; it has been estimated that the use of 

 hybrid corn in this country represents an 

 economic advantage of about a billion dol- 

 lars a year. Applications of the principles 

 of genetics produce superior domestic ani- 

 mals and farm crops. Also, research in hu- 

 man genetics is increasing our understanding 

 of the relation of hereditv to abnormalities 

 and diseases, both physical and mental. 

 Modern genetics is also giving insights into 

 the biological basis of human nature. 



HEREDITY 



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A knowledge of the reproduction and de- 

 velopment of animals provides a good foun- 

 dation for the discussion of heredity. In a 

 legal sense we may inherit lands, buildings, 

 and various articles; but we are not con- 

 cerned here with this type of heredity; we 

 are concerned with biological inheritance. 

 We inherit from our parents the potentiali- 

 ties for various traits (characteristics) that 

 can be observed, and the determiners of 

 many other characteristics that we never ex- 

 hibit. As a rule, when we discuss heredity, 

 we do not refer to those traits that are com- 

 mon to all members of a group or species, 

 but to variations in body and mental traits 

 that may be possessed by both parents and 

 offspring. Thus we are not ordinarily con- 

 cerned with the fact that both father and 

 son, each, have two eyes, but we are con- 

 cerned about the color and other charac- 

 teristics of their eyes. This is because the 



