Q.Explain the law of dominance in monohybrid cross.

The dominant Le allele encodes the enzyme that converts an inactive gibberellin precursor into its active form (GA1), producing tall pea plants.

Mendel's classic tall/dwarf pea trait has since been explained at the molecular level: the Le locus encodes an enzyme (GA 3beta-hydroxylase) in the gibberellin biosynthesis pathway. The dominant Le allele produces a fully functional enzyme that converts an inactive gibberellin precursor (GA20) into the biologically active gibberellin GA1, which promotes internode elongation and produces the tall phenotype. The recessive le allele carries a mutation that renders this enzyme non-functional or much less active, so le/le plants accumulate the inactive precursor but cannot efficiently convert it to active GA1, resulting in the classic dwarf phenotype -- a beautiful molecular confirmation of Mendel's originally purely phenotypic dominant/recessive model. Among the options, GA1 is the active hormo …