Example of Incomplete Dominance
If $AA=10$ & $aa=0$ then which of the following is the example of Incomplete dominance-
- $Aa=5$
- $Aa=7$ — Correct Answer
- $Aa=10$
- $Aa=15$
Explanation:
Correct Answer: Aa = 7 (Incomplete dominance)
In incomplete (partial) dominance, the heterozygote shows a phenotype between the two homozygotes but closer to the dominant. The midpoint = (AA + aa)/2 = (10+0)/2 = 5. Aa = 7 lies between 5 and 10 → partial dominance. It is NOT at the exact midpoint (5 = additive) and NOT equal to the dominant (10 = complete dominance).
Examples of Incomplete Dominance in Animals
- Feather colour in Andalusian fowl: Black (BB) × White (bb) → Blue/Splash (Bb) — classic incomplete dominance.
- F₂ phenotypic ratio: 1:2:1 (not 3:1 as in complete dominance).
All Four Gene Actions — Quick Reference
| Aa Value | Gene Action |
|---|---|
| = 5 (= midpoint) | Additive |
| = 7 (midpoint < Aa < AA) | Incomplete dominance |
| = 10 (= AA) | Complete dominance |
| = 15 (> AA) | Over-dominance |
📚 About this Topic — Animal Genetics & Breeding
This multiple choice question is from Animal Genetics & Breeding, Animal Refresher. It has 4 options with a detailed explanation of the correct answer. Practice more MCQs from Animal Genetics & Breeding to strengthen your preparation.
