138 HEREDITY AND SEX 



carried by the female-producing sperm. The analysis 

 is then as follows: One "dose" of horns (H) in the 

 male produces horns, but two doses are necessary for 

 the female. 



Hornless ? hX hX 



Horned 3 H X H 



Fi HXhX hornless 9 



H h X horned $ 



Gametes 

 of Fi 



Eggs HX hX 



Sperm HX hX H h 



- F 2 FEMALES F 2 MALES 



HXHX horned HEX horned 



H X h X hornless H h X horned 



hXHX hornless HEX horned 



h X h X hornless h h X hornless 



As pointed out by Punnett a test of the correctness 

 of this interpretation is found by breeding the FI 

 hornless female to a hornless male (of a hornless breed) . 

 It is assumed that such a female carries the factors for 

 horns in a heterozygous condition ; if so, then half of 

 her sons should have horns, as the following analysis 

 shows : 



Fi Hornless ? HX hX 

 Hornless $ hX h 



/* X # X hornless T 



h X h X hornless ? 



hEX horned <J 



hh X hornless c? 



