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HEREDITY AND ENVIRONMENT 



determiner. Sex and sex-limited inheritance 

 are only special cases of Mendelian inheritance 

 in which conditions of dominance differ in the 

 two sexes, depending upon whether the factor 

 for sex is duplex or simplex. 



Gametes 



Fi 



Fig. 58. Diagram showing sex as a Mendelian character, 

 the female being homozygous, the male heterozygous for sex. 

 The female forms gametes all of which contain the X 

 chromosome; the male forms two sorts of gametes one-half 

 of which contain the X chromosome and the other half lack 

 it. All possible combinations of these gametes give a 2:2 or 

 1:1 ratio of females to males. 



