Question

Two independent monohybrid crosses were carried out involving a tall pea plant with a dwarf pea plant. In the first cross, the offspring population had equal number of tall and dwarf plants, whereas in the second cross it was different. Work out the crosses, and explain giving reasons for the difference in the offspring populations. [3]

Answer 1

First Cross (Case I)
In the first cross between the tall plant and the dwarf plant, equal number of tall and dwarf plants are produced. This is because the tall plant is heterozygous dominant (Tt) and dwarf plant is homozygous recessive (tt). The progenies will be 50% tall and 50% dwarf. [1.5]

Second Cross (Case II)
In the second cross between the tall plant and the dwarf plant, all the offsprings will be tall. This is because the tall plant is homozygous dominant (TT) and dwarf plant is homozygous recessive (tt). [1.5]