102 



Genes in the X and Y Chromosomes 



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II 



III 



IV 



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Fig, 35. Human pedigrees, (a) Inheritance of crooked little fingers, 

 minor streblomicrodactyly, a simple dominant. (From Hefner in the 

 Journal of Heredity.) (6) Inheritance of the radial loop fingerprint pat- 

 tern on the right index finger, probably the result of a sex-linked recessive 

 gene. (From Walker in the Journal of Heredity.) In both diagrams, males 

 are indicated by squares and females by circles. Individuals that show 

 the trait in question are identified by black or solid squares or circles in 

 contrast to normals, who are represented by white or hollow symbols. In 

 human genetics it has become customary to place the male first in a cross 

 although in plant genetics the female is conventionally placed first. 



