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IX 



Heredity 



IT is truly a long step from tall and dwarf peas to human inheritance but 

 the gap is being bridged slowly and painstakingly. Almost every stu- 

 dent is interested in the genetics of hair color, of right or left handedness, of 

 color blindness, of hair blazes (white areas in otherwise colored hair), of 

 disease, of twinning, of intelligence and of musical ability, among other 

 things. A comparatively few years ago the knowledge of human inherit- 

 ance was fragmentary, inconclusive and scattered. At the present time 

 it is none of these things although it should be borne in mind that many 

 years must elapse before we know as much about this field as we know 

 now about the fruit fly, the favorite of animal geneticists. Dr. Gates has 

 recently brought together most of our knowledge regarding human in- 

 heritance into a two volume work and while this is a notable contribution, 

 it reflects the opinion that we know only a mere fraction of the knowable. 



With plants and the lower animals we are able to breed, cross-breed, 

 make chromosome preparations and use other intimate techniques, all of 

 which are impossible or difficult when using human material. Much can 

 be learned regarding the inheritance of human traits however by studying 

 pedigrees for some generations, particularly those where abnormalities 

 are in evidence or where the parents are of different racial groups. 



Almost every layman has one or more misconceptions regarding hered- 

 ity. Some of the more common errors are, (i) blood will tell, or, he is 

 of blue blood (2) listening to good music or good literature will create 

 a taste for these things in the unborn child (3) peculiar markings on the 

 skin of the child are caused by the sight of some animal or other object 

 which frightened the mother (4) the blood of the mother passes into and 

 through the child in the uterus (5) syphilis and gonorrhea are inherited 

 (6) two pure white people can have a black child (7) two blue-eyed par- 

 ents can never have a brown-eyed child (8) that environment is not impor- 

 tant in the development of a person's heredity and (9) that a child always 

 resembles the more strong-willed of the two parents. 



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