A Mendelian experiment consisted of breeding tall pea plants bearing violet flowers with short pea plants bearing white flowers. The progeny all bore violet flowers, but almost half of them were short. This suggests that the genetic make-up of the tall parent can be depicted as

(a) TTWW

(b) TTww

(c) TtWW

(d) TtWw

Why cannot it be (D) TtWw ? Why is it WW?

The genetic make up of the tall parent can be depicted as TtWW. Since all the progeny has violet flowers so the genotype of tall plant for violet flower color should be WW. Secondly, since almost half of the progeny is short which suggests that the tall plant is not pure and possesses the genotype Tt. 

So if the cross is made between the tall parent TtWW and other parent ttww, genotype of the progeny obtained is 

TtWw (8): ttWw (4): ttWw (4)

All the progeny bears violet flowers but half of them are tall and half are short.