322 



ELEMENTS OF BIOLOGY 



breed Tall through succeeding generations. Therefore, one-fourth 

 of the F2 generation were pure for the character of Tallness, as 

 one-fourth had been shown pure for Dwarfness. The remaining 

 half, when bred, behaved like the Fi generation, separating out in 

 the F3 generation as Tall and Dwarf in the proportion of 3:1. The 

 Dwarfs of the F3 generation again proved to be pure and the re- 



PA RENTS 



TT—^TT 



Tt—t-Tt 



TT Tt 



Tt 



Tt 



Tt 



TT 



TT 



TT 



TT 



TT 



TT TT 



Tt—tzTt 



TT Tt Tt tt 



TT 



TT Tt 



T'T"— r— jr 



TT TT TT TT 



Fig. 204. — Chart showing the behavior of Tallness (T) and Dwarfness (t) in a 



monohybrid cross in peas. 



maining three-fourths of the F3 generation that were Tall again 

 proved to be of two sorts, Tall, and Tall with the potential of 

 throwing Dwarf offspring. 



Mendel's Laws. We now may analyze a monohybrid cross: 

 The Fi generation are all Tall. To outward appearance the F2 

 generation is in the proportion of three Tall to one Dwarf; in po- 

 tential for characters in future offspring, the ratio is one Tall : two 

 Tall with Dwarf hidden : one Dwarf. By this experiment with 



