Genetic Basis of Heterosis and SCA
Heterosis and specific combining ability (SCA) are both caused by:
- Additive gene action only
- Non-additive gene action (Dominance + Over-dominance + Epistasis) — Correct Answer
- Both additive and non-additive gene action
- Linkage only
Explanation:
Correct Answer: Non-additive gene action
Both Heterosis and Specific Combining Ability (SCA) are caused by non-additive gene action (Dominance + Over-dominance + Epistasis).
Gene Action and Its Applications
| Gene Action Type | Associated Phenomena |
|---|---|
| Additive gene action (AGA) | Polygenic inheritance, General Combining Ability (GCA), Resemblance between relatives, Chief determiner of resemblance |
| Non-additive gene action (NAGA) | Heterosis/Hybrid vigour, Specific Combining Ability (SCA), Inbreeding depression reversal |
Note: Reciprocal Recurrent Selection (RRS) is used to improve both GCA and SCA and is more suitable for poultry selection.
📚 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.
