Explain Mendel’s law of inheritance.

After performing his breeding experiments on garden pea, Mendel postulated three laws called ‘Laws of Inheritance’. These are:

(a) Law of dominance

(b) Law of segregation or law of purity of gametes

(c) Law of independent assortment

● Law of dominance states that When two homozygous plants, with one contrasting character, is crossed, the character which is expressed in an F₁ generation is known as a dominant character while the character which is not expressed in an F₁ generation is known as recessive character.

● Example: If pure or homozygous tall plants (TT) are crossed with the pure homozygous dwarf plant (tt), then we obtain all the plants in an F₁ generation (100%) as tall plants.

● Law of Segregation or Law of Purity of gametes. According to this law, during gamete formation in the F₁ hybrid plant both the alleles are got separated from each other and goes into separate gametes.

● Hence, it is known as the law of segregation or law of purity of gametes.

● Each gamete contains only one allele for one character. Thus no mixing of characters, gametes are always pure.

● Example: If homozygous tall plant (TT) is crossed with the homozygous dwarf plant (tt), then all the offspring of F₁ generation are heterozygous tall plants.

● Law of independent assortment states that when two plants having two or more contrasting characters such as characters for example height of a plant and shape of a seed, are crossed then inheritance of one character is unaffected by inheritance of another character.

● In F₂ generation formation of plants like dwarf plant with yellow seed and tall plants with green seeds, show an independent assortment of characters.