Gregor Johann Mendel (1822 – 1884) was the first to carryout the study on the transmission of characteristics from the parents to the offsprings. He proposed that heredity is controlled by factors, which are now believed to be segments of chromosomes or genes.Mendel’s Experiments :Mendel performed experiments on a garden pea (Pisum sativum) with different visible contrasting characters. He worked on the following seven traits of garden pea:True breeding pea lines were obtained by continuous self pollination for several generations.Fourteen true breeding pea lines were selected as pairs, which were similar except for one character with contrasting traits.Artificial cross pollination (hybridisation) was performed on such varieties to obtain first hybrid generation known as the first filial progeny or F1.After hybridisation, the F1 generation so obtained resembled only one of its parents (say, all tall; no dwarf).When 2 plants from F1 generation were self pollinated, the second filial progeny or F2 generation was obtained.Revival of unexpressed trait (dwarf) was observed in some F2 progeny. Both traits, tall and dwarf, were expressed in F2 in ratio 3:1.Mendel proposed that something is being passed unchanged from generation to generation. He called these things as ‘factors’ (presently called genes).Factors contain and carry hereditary information.Alleles − Slightly different form of same factorMendel performed his experiments on Garden Pea and proposed three lawsLaw of dominance- According to this law, characters are controlled by discrete units called factors, which occur in pairs with one member of the pair dominating over the other in a dissimilar pair.Law of segregation- This law states that the two alleles of a pair segregate or separate during gamete formation such that a gamete receives only one of the two factors. In homozygous parents, all gametes produced are similar; while in heterozygous parents, two kinds of gametes are produced in equal proportions.Law of independent assortment- When two pairs of traits are combined in a hybrid, one pair of character segregates independent of the other pair of character. In a dihybrid cross between two plants having round yellow (RRYY) and wrinkled green seeds (rryy), four types of gametes (RY, Ry, rY, ry) are produced. Each of these segregate independent of each other, each having a frequency of 25% of the total gametes produced.

Gregor Johann Mendel conducted experiments on pea plants and proposed the rules of inheritance; based on his observations. Mendel observed that characters are often present in pairs. A pair of contrasting characters is called allele.(This I have saw in the notes of exell up)from my side :The first study of inheritance was done by Gregor Mendel on garden pea. He used a number of contrasting characters like round / wrinkled seeds, tall/ short plants, white/ violet flowers and so on.