MENDEL S EXPERIMENTS 



different stages of development. It will be seen that the one structure 

 of the seed contains parts of the parent generation (in the seed coat) 

 and parts of the offspring (in the cotyledons). 



TABLE 1 



MENDEL'S SEVEN CHARACTERS IN PEAS 



Mendel crossed these differing lines of peas and found that, in each 

 cross, the whole of the seedlings of the first fiHal generation, or Fj, 

 resembled one of the parents in respect of each of the character 

 differences. The type which appeared in the crossed plants he termed 

 dominant, and its latent alternative recessive. The dominant is the first 

 of the two alternatives for each character in Table i, but it is impor- 

 tant to note that the result is the same whichever way the cross is 

 made : reciprocal crosses are alike. 



The Fi was uniform, as uniform as the parents had been. A second 

 generation, Fg, was then raised from self-pollination of the Fj, and 

 in the Fg famihes the recessive types reappeared together -With the 

 dominants. But no transitional or intermediate types appeared 

 amongst them. Furthermore, the dominants and recessives were 

 always in the approximate proportion of three to one. The exact 

 proportion, of course, varied from family to family according to the 

 chances of sampUng. The examples of Table 2, showing the numbers 

 of plants with alternative cotyledon characters, illustrate the principle. 



The next question to settle was the breeding properties of the 

 different types, the dominant and the recessive, in the F2. F3 families 

 were raised from individual F2 plants by self-pollination. All the 

 recessives bred true, but only one third of the dominants did so. 

 For example 166 bred true for yellow cotyledons and 353 gave 

 yellow and green types again in the proportion of three to one. 



37 



