Sex Chromosomes and Sex-Linked Genes 



101 



7.19. Reciprocal matings using pure lines of Drosophila produce all wild-type F, from 

 wild-type by vestigial wings. What are the genotypic and phenotypic expecta- 

 tions if the F a $ of this mating is crossed with a white-eyed vestigial-winged 9 

 w being sex-linked? s ' 



7.20. Give two ways in which knowledge of sex-linked genes could be put to practical 

 use. r 



7.21. A normal man of blood type AB marries a normal woman of O blood type 

 whose father was hemophilic. What phenotypes should this couple expect in 

 their children and in what relative frequencies? 



7.22. The diagram below is a partial pedigree of the descendants of Queen Victoria 

 of England (II) which contains information regarding hemophilia only for gen- 

 eration IV. In this generation, the entire symbol is filled in if the person has 

 hemophilia. A heterozygote for hemophilia would have been represented by a 

 half filled-in symbol. Fill in the symbols of previous generations using this 

 system. & 



111 = Princess Alice 



112 = Leopold, Duke of Albany 



1111 = Irene 



1112 = Alexandra 



1113 = Alice 



III5 = Victoria Eugenie 



I VI = Prince Waldemar of Prussia 

 IV3 = Prince Henry of Prussia 

 IV8 = Tsarevitch Alexis of Russia 

 IV10 = Viscount Trematon 

 IV12 = Alfonso 

 I VI 7 = Gonzalo 



II 



IV 



HI ( )1 



-n. 



oooo 



12 3 4 5 6 7 8 



OBO 



9 10 11 



12 13 14 15 16 17 



(After J. B. S. Haldane.) 



