MEN DELI SM AND MUTATION 



337 



by T) which makes the resulting plant tall. The germ cells of the dwarf 

 plant carry something (t) causirg the dwarf condition. In the first 



n 



T T I 



PARENTS 



00 00 



Tt 



,,0000 



FIG. 129. A typical Mendelian cross between tall and dwarf peas, showing dominance 

 of the tall over the dwarf condition in the first hybrid generation (Fi), and the 3: 1 ratio of 

 tall plants to dwarfs in the second hybrid generation (Ft). At the right is shown the 

 corresponding distribution of the Mendelian factors for tallness (T) and dwarfness (t). 



hybrid generation (Fi) both factors are present, T coming from one parent 

 and t from the other, but T "dominates" and prevents the expression of 



