Let us represent the allele for tall height by T and that for short height by t. The parents of the F1 generation are TT and tt. After the first cross, the genotype of all of the members of the F1 generation is Tt. If these plants self polinate, the resulting genotypes will be TT, Tt, Tt and tt. Therefore, there is a 75% chance that the offspring in F2 is tall and a 25% chance that the offspring in F2 is short.
