A homozygous pea plant with round seed coat and yellow cotyledons is crossed with another homozygous pea plant having wrinkled seed coat and green cotyledons.
State the Mendel's principle involved in this cross.

Explanation

As all the `F_1` plants were with yellow cotyledon and round seed, so allele Y for yellow cotyledon is dominant over allele y for green cotyledon and allele R for round seed is dominant over allele r for wrinkled seed. The appearance of all the four possible phenotypic combinations in `F_1` in the ratio `9:3:3:1` is possible if the two pairs of characters are believed to behave independent of each other. Each pair of contrasting characters bear no permanent association with particular other character. Mendel formulated his second law from the conclusions drawn out of his di-hybrid experiments. The law of Independent Assortment States : When the two parents differ from each other in two or more pairs of contrasting characters or factors, then the assortment of alleles of one character is independent of assortment of alleles of other characters. Each member of an allelic pair may combine randomly with either of another pair during the formation of gametes.