The Laws of inheritance were derived on the basis of finding by Mendel. These laws are collectively called Mendelism. Law of Independent Assortment: When plants with two or more than two characters are crossed then expression of one character does not affect the expression of another character. Genes from a pair of alleles segregate and are free to combine with any other gene from any other pair of alleles. This is called law of independent assortment. Example: Let us take example of dihybrid cross between a plant with round and green seeds (RRyy) and another plant with wrinkled and yellow seeds (rrYY). Here roundness or smoothness of seeds and yellow colour are dominant traits, while wrinkles on seeds and green colour are recessive traits.
When these plants were crossed then all plants in F1 generation produced round and yellow seeds. When plants of F1 generation were allowed to reproduce, plants of F2 generation showed following traits in respective ratio: Round yellow : Round green : Wrinkled yellow : Wrinkled green 9 : 3 : 3 :1 The observation that roundness combines with either of the colours and roughness combines with either of the colours proves the law of independent assortment.
