Genetic Basis of Heterosis and SCA
Heterosis & specific combining ability (SCA) both are caused by-
- Non-additive gene action (Dominance + Over-dominance + Epistasis) — Correct Answer
- Additive gene action
- Both a & b
- None of the above
Explanation:
Correct Answer: Non-additive gene action (Dominance + Over-dominance + Epistasis)
Both Heterosis (hybrid vigour) and Specific Combining Ability (SCA) are caused by Non-additive gene action, which includes Dominance, Over-dominance, and Epistasis.
Gene Action Types and Their Uses
| Gene Action | Type | Used For |
|---|---|---|
| Additive Gene Action (AGA) | Additive | Polygenic inheritance, GCA, Resemblance between relatives, Individual selection |
| Dominance | Non-additive | Heterosis, SCA |
| Over-dominance | Non-additive | Heterosis, SCA |
| Epistasis | Non-additive | Heterosis, SCA |
Heterosis — Key Points
- Depends on extent of heterozygosity and non-additive gene action.
- Traits with low heritability show high heterosis.
- Maximum hybrid vigour is obtained in F₁ generation.
- Heterosis in F₂ is reduced by 50% due to inter-se mating.
- Commonly used in broiler, layer, swine, and sheep production.
📚 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.
