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Rules for the inheritance of traits:, Mendel’s contribution:, , The rules for inheritance of traits in, human beings are related to the fact that, both mother and father contribute an, equal amount of genetic material i.e., DNA to their offspring. So an offspring, will get two versions of that trait from the, two parents. Mendel worked out rules for, inheritance of these traits. Gregor, Johann Mendel regarded as the ‘Father, of Genetics’ performed his experiments, with garden peas (Pisum sativum) in the, garden behind his monastery. He, observed a number of contrasting, characters in garden peas and observed, , their inheritance., , Mendel’s, Experiment:, , Mendel started his experiment on, the pea plants. He conducted first, , monohybrid and then dihybrid, crosses

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Monohybrid Cross:, , The cross in which Mendel showed inheritance of, dominant and recessive characters is monohybrid cross., To observe inheritance of single pair of contrasting, characters., , Pure Puree, Tall Plants Dwarf Plants, , 1T tt Parents, ¥ v, T, , Cross t Gametes, , 7, {Genotype}, , Tt F generation All Tall Plants (phenotype), , Self pollination, , |, , Gametes, Male/Female | 7 t, , 4 , , , , , T mT | t%, , , , t Tm tt, , , , , , , , , , , , He took pure tall (genotype TT) and pure dwarf, (genotype tt) pea plants and cross pollinated them to, obtain first generation or first filial generation. In this, figuration (F1 generation) he obtained only tall plants., , This meant that only one of the parental traits was seen,, not the mixture of the two. The plants of F generation or, progeny are then self pollinated to obtain F2 generation, or progeny. Now all plants were not tall. He obtained, 75% tall plants and 25% dwarf plants i.e. the phenotypic, ratio was 3:1. This indicates that in the F, generation, both tall and dwarf traits were inherited but tallness, expressed it self. Tallness is a dominant trait and, dwarfness is a recessive trait. F2 generation has a, genotypic ratio of 1:2: 1 of three types of plants, represented by TT, Tt and tt as shown in the cross.

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Conclusion:, , Phenotypic ratio—Tall: Dwarf 3: 1, Genotype ratio—Pure Tall: Hybrid Tall:, Pure Dwarf 1:2: 1, , Law of Dominance:, , When parents having pure contrasting, characters are crossed then only one, character expresses itself in the Ft, generation. This character is the, dominant character and the, character/factor which cannot express, itself is called the recessive character.