DOMINANCE AND THE 3:1 RATIO 



355 



this is not the case. When a tall pea is crossed with a 

 short one the hybrid is as tall as the tall parent and 

 ordinarily indistinguishable from it. In such cases " tall " 



Parent A 



Parent B 



The nuclei of the 



parents showing one 



chromosome pair with 



same gene in each chro 



mosome of the pair. 



Nuclei of the gametes pro- 

 duced by these parents with 

 only one chromosome 

 of the pair. 



Nucleus of the hybrid 



with the two chromosomes of 



thfe pair having different genes 



for flower color, (above) 



Nucleus of one 



kind of gamete 



produced by hybrid 



Nucleus of the 



other kind of gamete 



produced by the hybrid 



Fig. 99. — A diagram to show the segregation and combination of 

 chromosomes in hybrid pink four o' clocks. 



