In one of his experiments with pea plants Mendel observed that when a pure tall pea plant is crossed with a pure dwarf pea plant, in the first generation, `F_(1)` only tall plants appeared.
(i) What happens to the traits of the dwarf plants in this case?
(ii) When the `F_(1)` generation plants were self-fertilised, he observed that in the plants of second generation, `F_(2)` both tall plants and dwarf plants were present. Why it happened? Explain briefly.

Explanation

(a) Mendel crossed tall pea plants with dwarf pea plants.

Mendel.s Observation
The `F_(1)` generation contained all tall plants. When `F_(1)` generation underwent selfing, the trait that was unexpressed in `F_(1)` (dwarf) was observed in some `F_(2)` progeny. Thus, both traits, tall and dwarf, were expressed in `F_(2)` generation in the ratio 3: 1.
Mendel proposed that something was being passed unchanged from generation to generation. He called these things factors (presently called genes). Factors contain and carry hereditary information. He also observed that traits might not show up in an individual but were passed to the next generation.
(b) The two contrasting traits other than height used by Mendel are :
(i) Pod colour : Green pod colour dominant over yellow colour
(ii) Seed shape : Round seed shape dominant over wrinkled seed shape.