Question

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

Hint:

Incomplete dominance and co-dominance are exceptions to Mendel’s law, showing non-Mendelian inheritance patterns.

Answer 1

Law of Dominance: Mendel’s law states that in a heterozygous condition, one allele (dominant) masks the expression of the other (recessive) in the phenotype. Example: In pea plants, tall (TT or Tt) dominates dwarf (tt). Comparison: \[ \begin{tabular}{|l|l|l|l|} \hline Feature & Dominance & Incomplete Dominance & Co-dominance
\hline Definition & Dominant allele fully masks recessive & Neither allele fully dominant; blended phenotype & Both alleles fully expressed
Example & Tall (Tt) in pea plants & Pink flowers (RW) in snapdragons & AB blood group (I\(^A\)I\(^B\))
Phenotype ratio (F2) & 3:1 (e.g., 3 tall: 1 dwarf) & 1:2:1 (e.g., 1 red: 2 pink: 1 white) & 1:2:1 (e.g., 1 A: 2 AB: 1 B)
Expression & Only dominant trait visible & Intermediate trait & Both traits visible
\hline \end{tabular} \]