Explain the inheritance of shape and colour of the seed of pea plant (Pisum sativum).

Explanation

Mendel selected two characters in garden pea (Pisum sativum) for the study of inheritance, the shape and the colour of the seed.

Mendel selected yellow and round seeded plant as one of the parent (P) and crossed it with a green and wrinkled seeded plant as other parent (P).
In `F_(1)` generation all the plants showed yellow and round seeds, i.e., the yellow colour and round shape of the seed are the dominant characters. While the plants of `F_(1)` generation (having yellow seeds and round shaped seeds) when reproduced by self-pollination or self-fertilsation, four different combinations were observed in `F_(2)` generation : (1) Yellow and round seeded, (2) Green and wrinkled seeded plants, (3) Yellow and wrinkled seeded plants and (4) Green and round seeded plants.
This explained that the seed colours yellow and green and seed shapes round and wrinkled are inherited independently from each other.
Yellow colour is due to dominant Y and green colour is due to recessive y gene/allele. Similarly, R is dominant and it produces round seed shape, while r is recessive gene which gives rise to wrinkled seeds.