Solution:

Through his dihybrid cross experiment, Mendel demonstrated that characteristics are inherited independently. He used two traits in his experiment, namely seed shape and seed colour. Yellow (YY) has the upper hand over green (yy), while the round form (RR) has the upper hand over the wrinkled shape (rr). The dihybrid cross’s F2 progeny had a phenotypic ratio of 9:3:3:1. Hence, 9 plants had round yellow (RRYY) seeds. 3 plants had round green (RRyy) seeds. 3 plants had wrinkled yellow (rrYY) seeds and one plant had wrinkled green seeds (rryy). He went on to say that the wrinkled greens and round yellows are parental combinations. But the round green and wrinkled yellow are brand new. A dihybrid cross between two seeds with dominant (RRYY) and non-dominant (rryy) characteristics produced four different types of gametes (RY, Ry, rY and ry). This indicates that each gamete segregates independently of the others, with each segregating at a rate of 25% of the total gametes generated.