Q.Explain the law of dominance and compare how it differs from incomplete dominance and co-dominance.

The law of dominance states that in a heterozygote carrying two contrasting alleles, only the dominant allele is phenotypically expressed while the recessive allele's effect is completely masked (e.g.

The law of dominance masks the recessive allele entirely in a heterozygote, whereas incomplete dominance blends both alleles' effects and co-dominance expresses both alleles fully and separately.

Mendel's law of dominance states that when an organism is heterozygous for a gene (carrying two different alleles), only one of the alleles — the dominant one — determines the observable phenotype, completely masking the effect of the other, recessive allele; thus a heterozygote (e.g. Tt) is phenotypically indistinguishable from a homozygous dominant individual (TT), both appearing tall in Mendel's pea experiments, with the recessive short trait only reappearing in individuals that are homozygous recessive (tt). Incomplete dominance is a departure from this law: here, neither allele is completely dominant over the other, so the heterozygote displays a phenotype that is intermediate between the two homozygous parental phenotypes, essentially a blend of both — the classic example is a cross between red-flowered and white-flowered snapdragons (Antirrhinum), which produces pink-flowered F1 heterozygotes rather than all-red or all-white offspring. Co-dominance is a different kind of departure: here, both alleles in the heterozygote are fully and independently expressed at the same time, each contributing its own distinct, separately visible phenotypic effect rather than blending into an intermediate — …