Question

What is Mendelism? Explain the law of independent assortment.

Answer 1

Mendelism: The inheritance of traits from parents to the offsprings in a dominant-recessive manner is 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: The 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 $F_1$ generation produced round and yellow seeds. When plants of $F_1$ generation were allowed to reproduce, plants of $F_2$ 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.