As we all know Mendel is called as father of genetics. This title is given to him because he was the first man who postulate some laws of inheritance. i.e. how characters are move from one generation to other.
He given his postulates quite early and at that time almost no other one was working on same topic. Because of this this postulate remain unnoticed for a large time, some around 34 years. After word when other scientists performed the same experiment and end up on the same postulates as were given by mendel, it come to know to world that Mendel has studied and gives the law of inheritance. And he was giving credit of his work.
Till today there is almost no exception found in the Mendel’s first law of inheritance, which is “Law of Dominance”. So, it is also known as the universal law of inheritance.
Mendel’s first law of inheritance i.e. law of dominance, is base on monohybrid cross. While studying this law mendel considered only one character of pea plant. This character was the height of pea plant. While crossing between plants, mendel considered tall and short pea plants.
Mendel considered the height of pea plant long pea plant is called to have pure traits of tallness and contain both the allele in pure form (represented by ‘TT’). However, short plant is also a pure bread of short plant i.e. contain both the allele in pure short form (represented by ‘tt’)
When theses pure breed plants are crossed then the coming generations show the trait of dominant gene, they got from their parents. However, genetically they are heterotrophic i.e. having one allele of pure tall and other allele of pure short plant (Tt type of genotype). And phenotypically they all show the trait of dominant allele (T).This law suggest that when dominant allele is present in the cross, it suppress the receive character allele and express itself phenotypically.