Mendel crosses varieties of pea plants that differed in more than one characters from each other by two pairs of genes. This is called dihybrid cross. By performing this cross he stated the law of independent assortment which explains that alleles of different genes are assorted independently of each other at the time of gamete formation. In monohybrid cross produces two phenotypes (3:1) whereas dihybrid cross produces four phenotypes in the ratio of 9:3:3:1. This 9:3:3:1 ratio also shows that the two different genes independently express the phenotypic ratio of 3:1 each. This proves that all the traits in an organism are inherited independently.
Inherited traits: The traits or characters that are passed from parents to their children by the genes are termed as inheritance. E.g. eye colour, hair type etc.
Acquired Trait: These are the characteristics that are acquired by the organisms in their lifetime, to survive successfully or in a better way. These characteristics are not transferred to the next generation. For example, large muscle size of a person is acquired by doing exercise and cannot be passed to the next generation. It is an acquired character.