Explain the law of dominance in monohybrid cross.

Explanation

The characters are controlled by discrete units called factors or genes. If a pair of dissimilar factors are present in one allele, one factor of the pair dominates over the other in phonotype expression of a particular character. The factor which dominates over the other factor is called dominant factor or gene and the other is recessive.
Monohybrid cross: Mendel took a single character such as plant height for monohybrid cross. Monohybrid inheritance is the inheritance of sinlge character.
Mendel crossel a tall pea plant with a homozygous short plant and he got only tall plants in the `F_(1)` generation. When the `F_(1)` generation was selfed he noticed that 787 of 1064 of `F_(2)` plants were tall and 277 of 1064 were dwarf. The dwarf trait disappeared in the `F_(1)` generation and appeared in the `F_(1)` generation.
The law of dominance gives an explanation to the monohybrid cross is the expression of only one of the parental characters in `F_(1)` generation and the expression of both in the `F_(2)` generation. It also explains the proportion of 3:1 ratio in the `F_(2)` genration as follows:

The gene for plant height has two alleles such as tall (T) and dwarf (t) and in `F_(1)` generation the hybrid is formed with the genotype Tt, where both the genes are present. But all the plants produced in the `F_(1)` are found to be phenotypically tall, indicating the tall character dominate over the dwarf nature, but it reappears in the `F_(2)` generation.