CHAPTER XVIII 



DROSOPHILA TYPE AND POULTRY TYPE OF SEX-LINKED 



INHERITANCE 



1. Drosophila type. The same type of sex-linked inheri- 

 tance which is found in Drosophila is found also in man, in 

 cats (inheritance of yellow color), and in the plants, Lychnis 



Fig. 120. Sex-linked inheritance of barred and of unbarred (black) plumage in poultry. P, parents, 

 barred male, unbarred female; Fi, barred males and females; F2, males all barred, females in equal 

 numbers barred and unbarred. (After Morgan.) 



and Bryonia. The essential feature of this " Drosophila 

 type " of inheritance is this. In a race breeding true for a 

 sex-linked character, the female is homozygous for the 

 character in question while the male is heterozygous and in- 



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