Question

What is incomplete dominance ? Give an example.

Hint:

In incomplete dominance, the {Genotypic ratio} and {Phenotypic ratio} are exactly the same (1:2:1).

Answer 1

Step 1: Understanding the Concept:
In Mendelian inheritance, one allele is usually dominant over the other. However, in incomplete dominance, neither allele is completely dominant.
Step 2: Detailed Explanation:
Mechanism: When a cross is made between two parents with contrasting traits, the heterozygous offspring expresses a blended or intermediate trait.
Example: Flower color in Antirrhinum (snapdragon) or Mirabilis jalapa (4 o'clock plant).
1. Cross: Red flower (RR) $\times$ White flower (rr).
2. $F_1$ Generation: All flowers are Pink (Rr).
3. Phenotypic Ratio in $F_2$: 1 Red : 2 Pink : 1 White.
Step 3: Final Answer:
Incomplete dominance results in an intermediate phenotype in heterozygotes. A classic example is the pink flowers produced by crossing red and white snapdragons.