Question

When Mendel crossed true-breeding tall pea plants with true-breeding short pea plants, all the offspring were tall. Then he allowed the first generation tall plants to self-pollinate. What were the ratios of phenotypes he expected in the F2 generation?

Answer 1

Answer:

3:1

Explanation:

Let the allele for tall plant be T;     &

The allele for short plant be t

When Mendel crossed true-breeding tall pea plants(i.e TT) with true-breeding short pea plants(I.e tt); all the offspring were tall.

TT  ×  tt

                     T                    T

t                    Tt                    Tt

t                   Tt                     Tt

we can deduce from the punnet square that the F1 offspring are all heterozygous tall plant.

Now, if the first generation (F1) tall plants are allowed to self-pollinate; we have a cross between Tt and Tt

TT  ×  tt

                     T                    t

T                    TT                    Tt

t                     Tt                     tt

We can see phenotypically that we have 3 tall plant(TT,Tt, Tt) and 1 short plant(tt).

Therefore the ratio of phenotypes he expected in the F2 generation is (3:1)