40 



TYPES OF MENDELIAN HEREDITY 



not occur, but if the flies are reared on dry food they 

 are normal from the beginning. The character is a 

 sex linked dominant, as shown by the following 

 crosses. When an abnormal male is bred to a normal 

 (wild) female, the daughters are abnormal (if the 



Fig. 19. — Mutant type called Abnormal Abdomen of Drosophila 

 ampelophila (the wings have been cut off); ais female; b, male; c, female 

 that approaches the normal type. 



food is moist) , but all the sons are normal. If the 

 medium is dry, however, both the daughters and the 

 sons alike are normal. But these normal F i daughters 

 will produce the expected abnormal offspring if the 

 conditions are suitable, and these offspring are just as 



